In Britain, Bob Hoskins is used to being a household - well, you can't quite say face, because that round head, squat body and stumpy legs are all essential to the total, inimitable effect. ''Five-footsix cubic,'' he calls himself, and five-foot-six cubic he is - a chunky, human bullet made of gristle and bone, and, since he played the sleazy sheet-music salesman in the original television version of ''Pennies From Heaven'' four years ago, well enough known to his fellow Londoners to be regularly accosted in park, subway and street. His fame has spread overseas as well - ''The Long Good Friday'' is playing in American film houses, and his most recent television venture, ''Flickers,'' is currently being shown on public television.

Mr. Hoskins's earthy, ebullient image helps, too. He's the local boy made good, an ordinary bloke with Falstaffian charisma: smaller than average, yet larger than life, and somehow the more approachable for being so. ''People behave as if they've known me for years,'' he said. ''A geezer came up to me the other day and said, 'Look, you've gotta talk to my Maureen. She don't listen to me, she'll listen to you.' Well, I was prepared to talk to Maureen, but then he suddenly realized he didn't actually know me, and got embarrassed and went away.''

Mr. Hoskins enjoys telling stories like that, especially if he's sitting in a pub at the time, and especially if that pub is in what he calls his ''manor,'' meaning Holloway and Finsbury Park, a mainly working-class stretch of northeast London. Indeed, he readily admits to enjoying most of the things he does. He enjoys the theater (''It's my religion''); he enjoys his fellow actors (''A real performance is as much a shock to the system as a minor road accident, and when I see some old guy acting his socks off, I'm proud to be in the same profession''); he enjoys being on stage or screen himself (''When it's really flying up there, really cracking between you, it's the most thrilling relationship in the world'').

He enjoyed New York when he visited it recently: ''Like the East End, only with taller buildings.'' And he most certainly enjoys the American success brought him by the film ''The Long Good Friday,'' in which he is a London gang leader, and the television series ''Flickers,'' in which he plays an aspiring entrepreneur in the embryonic movie industry of 1910: ''Yeah, here I am, sitting in a boozer in north London, and at this very moment in New York and L.A., people are talking about me. Me!''

''Me'' looked destined for disaster a mere 15 years ago. At age 25 he was, he says, a bum and a drifter, ''totally, absolutely lost - everybody said I'd end up on the gallows.'' What happened next is already something of a legend. He was downing double whiskies in the bar of an amateur playhouse when someone mistakenly shoved a script into his hand, declaring, ''You're next''; he found himself blearily auditioning for the lead in the next production (''It was a yob, it was me''), got the part, and was seen by a theatrical agent; within weeks he was in professional out-of-town rep, and within three years was at London's prestigious Royal Court, playing a 40-minute scene in Charles Wood's ''Veterans'' with John Gielgud.

On-the-job experience was and remains Mr. Hoskins's only training as an actor; but he has, he insists, worked with and learned from the best. Mr. Gielgud it was who told him how to get a laugh from a line that was falling flat. ''Step back two paces, dear boy,'' advised the great man. ''Then count to two, then say it.'' Mr. Hoskins did precisely that with words that were worrying him in ''Veterans'' and the result was, not just laughter, but nightly applause.

Mr. Hoskins's part in ''Veterans,'' a play about the shooting of a movie, was a salty-tongued cockney - which is not only what he himself was but what he has always been careful to remain, notwithstanding the pressures to change that he has inevitably met in class-bound Britain. He is still a dedicated Doolittle, despite the efforts of several would-be Higgins's: ''There was a time when people said, 'You've got to speak like you don't, walk like you don't, be like you aren't.' I said, 'Ere, 'ang on, who am I? I'd be lost if I did that. I'd be disappearing. I'd be ectoplasm.

''My accent, it's my identity, it's me. And that's why I swear a lot, too. It's a kind of snobbery, a kind of pride. I like the way I talk. I like the way I am. I think I'm all right. I'm happy with me. I'd be happy to meet me. It's a matter of integrity, you see, and of necessity. Whoever I play onstage, whoever I become, I must have a starting-off point. I must be sure of who I am, so sure it doesn't worry me, before I become someone else.'

It goes further than that, too: ''This part of London is where I was born, where I was brought up, where I live, where I'm at home. I'm happiest among costermongers and that. Nobody's impressed by me here. I don't want to lose the street, because that's what I relate to and where I act from.''

In other words, it would be as much against his professional interest as against his personal instinct to allow success to suck him into the suburban or ex-urban middle-class. That is why he has persuaded his bank manager -a long-suffering gentleman who still allows the permanently debt-ridden Mr. Hoskins no more than $100 a week pocket money - to lend him enough to acquire a ramshackle house just round the corner from Holloway Prison and barely a mile away from where the actor's parents still live.

From that background and that environment, Mr. Hoskins believes, comes an energy that infuses his performances, whatever the status or nationality of the character he is playing: Richard III, Iago, Bosola in Webster's ''The Duchess of Malfi,'' Lee in Sam Shepard's ''True West'' or, his current success at the National Theater, Nathan Detroit in ''Guys and Dolls.''

He likes to think that his range is larger than his physique might suggest: ''If someone were to offer me a script I didn't think I could do, that would be a total attraction to do it.'' In any case, he believes that he can actually, if invisibly, alter his appearance when the occasion demands. In the National's production of ''True West,'' for example, Mr. Hoskins played the rougher and more forceful of two brothers, and Anthony Sher, the more intellectual and weak.

''My throat changed shape, my voice changed shape, my head changed, my thighs changed, I changed,'' he insists. ''I'm three inches shorter than Tony Sher, and everybody told me I was taller. The audience sees the aura, the psyche you're projecting, not a fivefoot-six actor.''

Of course, such changes can only occur when the interpretation is right. Mr. Hoskins insists that the first question he asks when offered a play or movie is who his fellow actors are and where it is to happen: ''Is it going to be a merry time with a bunch of merry people, preferably on location in Barbados?''

But this characteristically Epicurean approach doesn't mean he isn't also serious and thorough when it comes to exploring and preparing a part. ''You gotta begin by finding the man's problems and analyzing them,'' he says. ''What he wants, what he hates. His pain, his humiliation, his pride. Then you let the part demand what it demands. You don't tamper, you don't get too intellectual. You let it grow, like gardening, like a flower. By the end you should be right in it, living it and not aware of your real self at all. When I was doing 'Pennies From Heaven,' I was convinced I looked like Fred Astaire, tall and slim and all that. I was horrified when I saw this little guy strutting about the television screen.''

Throughout the preparation process, Mr. Hoskins does his private research and feeds in any information he garners. Once he nearly blinded himself with a starter's pistol in order to find out what the wounded soldier he was playing might be feeling. For his Iago in the recent BBC-TV ''Othello,'' he went to live in the house of his director, Jonathan Miller, who is a qualified doctor with a special interest in mental problems; out of their discussions came a smiling psychopath. ''His emotions are gray, he feels no kindness, he wants to create chaos just for a laugh,'' Mr. Hoskins recalls. ''I found it a very frightening thing to do. So did Jonathan's family. He told them, 'We've got a psychopath coming to stay for a while.' The temptation was there to cause all sorts of trouble for them. But I'm glad to say I didn't.''

Arnie Cole, the anti-hero of ''Flickers,'' he thinks a ''wonderful, flamboyant character, the sort most people would give their eyeteeth to play. He's totally and utterly straight, he never changes, he never kids anyone, and yet there's so many conflicts there - he's a restless megalomaniac, a spiv, a man of vision and also of tenderness.'' A sense of northeast London and its streets was, he thinks, particularly important in the creation of the character. Indeed, he called on several acquaintances he'd made when, in his misspent youth, he briefly worked as a circus fire-eater: ''I talked to them, went round the fairgrounds, even did a bit of touting myself.''

The Hoskins philosophy is ''what you're doing at the moment is the most important thing. If you don't want to do it, get out. And if you do, give yourself to it absolutely and entirely.'' Just now that means giving himself to ''Guys and Dolls,'' as substantial a hit as the National Theater has ever scored and an experience that Mr. Hoskins himself has enjoyed as much as any: ''It's a real ensemble. Everyone's getting a good wage, no one's getting a ridiculous one. People aren't cut off from each other by money, and no single performance is all-important, certainly not mine. Come to think of it, that's probably the secret of my success - I've always been part of a good show, never all of a bad one.''

But what will he do when he leaves ''Guys and Dolls'' in August? Well, it's another article of the Hoskins faith never to take much thought for the morrow. Careers aren't to be mapped out. Things are simply to be allowed to happen. Mr. Hoskins's only firm plan right now is to be, if you'll believe it, a paraplegic hang-glider in a television play by his friend and fellow-actor, Gawn Grainger. Perhaps he'll take the lead in a movie about the pioneer of British slapstick, Fred Karno, which is at present being set up by John Mackenzie, who directed him in ''The Long Good Friday.'' Conceivably, he may be seen onstage as Fungus the Bogeyman, the spectacularly repellent hero of a series of children's books: ''He's got big, pointed ears. He's evil, just like me.''

Stage, screen and television - Mr. Hoskins declares himself equally happy with all three, equally determined to continue performing on them all and only wishes someone would invent a fourth medium in which he could enjoy himself as much: ''It terrifies me when I think what might have happened to my life if I hadn't walked into that bar that day and got that audition. The luckiest thing that ever happened to me was getting into this business. Every job that comes up, I love it. It's bleeding marvelous.''

Copyright 1982 The New York Times Company  
The New York Times