SHE was the little girl that Britain would never let grow up. She made twenty-five films in her early years--most of which she would rather now forget--but when the child star became a woman there seemed to be no place for her.       Things got to such a point that Pet decided to give it all up. Go off round the world. Anywhere. But she just had to get away to start again, to change everything.       The next chapter in the Petula Clark story reads like a Holly- wood scenario. She met Claude Wolff, a French music publicist. They mated and started a family. Claude took charge of her business affairs and her career. And from that moment on Pet was a changed woman. Her career has never looked back.      Today Pet Clark is a sophisticated pop star, an international cabaret artist, and about to be seen again in a major Hollywood movie. All credit, says Pet, is due to her husband. She finds it hard to believe that she was ever the little girl that   generations of British filmgoers still remember. `It all seems so distant, and vaguely in the past' It Is only here that she is reminded of her past career, for her new fans in other lands never saw the early films.      Just before she started work on her BBC-1 series Pet had a one-day stop-over in London to make a new record. She had come from Paris, and the next morning she was off on her way back to Hollywood where she had left her children.      She welcomed me to her suite at her Bond Street hotel. In the corner lay the symbol of her life today, an open half-packed suitcase. Tucked rather sadly on top were two string-tied brown-paper parcels-presents for Bar- bara and Catherine.      It's often a lonely world when you're a travelling star. True, everyone wants to see you, producers, recording men, the press, but the personal loneliness is still there.      Her husband shields her from this glare - sometimes perhaps too   efficiently - for on this day the person at the centre of the Pet Clark industry lunched alone. In the scamper to fix deals Claude had called every- one into an all-day meeting. And Pet, not to be disturbed, was left alone.      For the evening she was booked from six o'clock until midnight in a recording studio making her new single. We had an hour to talk before she began rehearsals. The next morning the plane left London Airport for America at 11.0 a.m.      She sat on the brightly coloured sofa. She was wearing a black woollen mini-dress, with a dazzling gold chain around her waist. Smaller than you expect, blonde with huge sparkling eyes, and flutter lashes. She leant forward and talked for a moment- about the debit side of being a star.      `In this business you are so busy projecting yourself, I guess that's the word, that you miss those lovely quiet moments when there is absolutely nobody around. When you can lie onthe grass and watch the ants. Things like that. I can't remem- ber when I last did it. I'd like to do that again.      Look at the ants, and the leaves, and the grass. After a while Hollywood, Paris, London, Rome, and all that rushing about.. . it doesn't matter at all. I want to get down to looking at things again. Right now, that's very important to me.      I'm really happiest when I'm on the stage, I suppose, completely free of all troubles, and I can just let myself go. I love to sing. I would never, never, never give that up.'      She talks with a slow, gentle voice with just a hint of an Irish accent. This is a hangover from her part in Finian's Rainbow. `At the end of the film Fred Astaire, Tommy Steele, and I were all using rich Irish brogue. It's very hard to stop now.'      Does she think that she works too hard?      Sometimes I think so. Most of the time I don't have time to think whether I'm working too hard   or not. I always make sure that. I have time to see the children.      They were with us in Los Angeles when I was making Finian's Rainbow. Sometimes they weren't up when I left, but I knew they were there. I could go home and put them to bed, and ring them up during the daytime, and sing them songs. It's going back to an empty house which is so awful.'      What is it that stops her throwing up her career and just being a mum at home?      I've thought about it, of course, and little things they say, and sometimes I wonder if I should go on. But they're really very happy. I don't know If I could be completely happy giving up my career, and I don't think it would be good for them having an unhappy mother. We're a very happy family the way we are.      `If I ever saw that our children were suffering, becoming unhappy because of my work, I would give it up. I really would, there is no question about that They really do   come first in our lives.'      Talking about Pet's children, you have found the warmest side of her. She speaks from the heart, sometimes perhaps close to tears when recalling some of their childish antics and sayings. She is not the big Hollywood star, but a woman and a very tender mother. This is what she has been trying to tell everyone for years, but the explanation was too simple and uncomplicated for the world to listen.      What about show-business careers for her two daughters?      `I hope not,' said Pet firmly but I can see already that the little one is the raw material fat a star. She is just outrageous she was born a beatnik, as wild as they come.      She is determined to keep her children as `un-showbiz' as possible. She steers the professional side of her life siell away from them. `When I'm giving interviews or having my picture taken they know that they have to leave the room. They don't stand around listening or posing. They're not like that. I never, ever let them stay up late.      `I remember once in Montreal when I was doing a one-woman show they came to a matinee and during the interval they came round backstage and the little one said: "Mummy, we've just seen Mummy on the stage." They know that as soon as I am in their presence I am all theirs, and they are are mine. That's the only way I can cope. It's difiicult, but just possible.'      Pet is not the least starry- eyed about her film career. She had just signed a contract to appear in the musical version of Goodbye Mr. Chips with Peter O'Toole, `my biggest break ever.'      But she is not at all dazzled for she speaks with the authority of someone who has seen it all before. `I know that it's a very shaky thing being up there. What I'd like to do is one film a year, and a few concerts around the globe. I discovered that we spend more time in other people's houses and rented houses than we do in our   own, and I'd like to see that end,`And the rest of the time I'd just like to be me, whoever that is.'      Her London manager, Martin Wyatt, arrived to take her to the recording session. She put on her black fur mini-coat and came out into the lift.      She was laughing as she ducked out into the London drizzle. A happy, contented woman, but a little incomplete without her two daughters whom she loves-and needs.