But Lord Longford and Mary Whitehouse turned up at the screening in Wardour Street, Soho, to condemn it. They saw the film - which included a shot of a teacher masturbating - as pornographic smut that would corrupt the nation's youth. Dr Cole saw it as a contribution to improving sex education.
It was a contribution that few schools outside London felt inclined to accept. In Birmingham, where Dr Cole still lives, it was banned by the education authority. His reputation had preceded him. 'Sex King Cole' the tabloids called him.
They had laid siege to his handsome Victorian home behind a high hedge in respectable suburbia. Then, as now, it was the headquarters of the Institute for Sex Education and Research. And then, as now, it was the only place in the UK where men with problems relating to impotence or premature ejaculation could be offered what might be termed 'on the job' help from sympathetic female strangers. 'Surrogate partners' Dr Cole calls them.
Dame Jill Knight, MP for Birmingham Edgbaston, had another word for them in 1972. 'He's more or less running a brothel,' she proclaimed.
Dr Cole had always wanted a career very different from that of his father, a Pooterish clerk who used to travel by tram every day from the family home in Enfield, north London, to the Bank of England. 'My parents brought me up very strictly and fed me enough guilt to last me a lifetime. But I remember vowing that my life would not be like theirs.'
It could hardly have been more different. A first-class honours degree in biological sciences at Southampton University was followed by a PhD ('I was sublimating my sexual energies in hard work'). He then went to Africa to teach medical students before returning to take up a post at Aston University in 1964.
It was then that the rebellion against his parents' values began in earnest. Over the next few years, he campaigned for the legalisation of abortion, helped to set up the first Brook Advisory Service on contraception outside London and founded the British Pregnancy Advisory Service.
'We had been through the dark ages,' he explains, 'and I was concerned about sexual freedom.' When asked if he had enjoyed his notoriety, the smile that is never far from his lips broadens into a grin. 'I must have done.'
The ageing process has not dulled his appetite for work. He still gets up at five every morning to concentrate on his writing before the first client arrives.
He has just updated his 1989 book Sex Problems - Your Questions Answered for a second edition retitled Sex - why it goes wrong and what to do about it when it does, to be published by Optima in December. And he is embarking on another book that should encompass every aspect of his experience of over a quarter of a century of grappling with other people's sexual problems. Britain has become a far less sexually repressed society in that time, but some things have remained constant. The most common complaint he is still asked to deal with is the man who has trouble achieving or sustaining an erection. 'The causes might have changed. A lot of middle-aged men are on medication that can affect them.
'When we started, there was an assumption that in 95 per cent of cases the cause was psychological. In fact, about 50 per cent are caused by medical conditions that can usually be treated.'
The remainder lack confidence. Either they are virgins in their late twenties or thirties ('there are still quite a few around') or they are betwen 40 and 55 and have suffered bereavement, divorce or separation.
'They might not have slept with anyone for several years, but they have found a new partner and they are anxious about their performance. Not surprisingly, they fail. There's been a sharp increase in this sort of referral because of the high divorce rate.'
Since 1972, between 400 and 500 have been 'prescribed' treatment with a surrogate partner. When Dr Cole started the practice, there were 10 surrogates. Now there are just two. The threat of Aids has deterred prospective volunteers.
'We do take every precaution,' says Dr Cole. 'Condoms are always used and there are regular tests for HIV.'
But where does he find these women?
'Usually they've read about me in one of the women's magazines and rung me up.
'They have to be intelligent and uninhibited and not bear any hostility to the opposite sex. Not too unattractive, though that's not a major factor, and not too young. Most have been between 30 and 45, though I have employed them in their fifties.'
Clients pay pounds 95 for a session with a surrogate partner. How does he know that some men are not just feigning problems to use the service as a form of prostitution?
'You can easily tell if someone's trying it on. I was conned only once by a journalist from the News of the World who put on a very convincing performance.'
But before the reporter got to the position where he could make his excuses and leave, Dr Cole received a telephone from a neighbour pointing out a tele-photo lens trained on his window from a car outside.
Dr Cole has been known to use male surrogates for a few female clients. But he has noticed a subtle change in the problems brought to him by women. 'In the Seventies and early Eighties it was usually because they couldn't have orgasms with their husbands or partners.
'They'd all read articles in Nova or Cosmopolitan explaining how to do it by numbers and they'd all been told that any woman can have an orgasm if it's done properly. Obviously that raised expectations.
'Now we know that only about 50 per cent of women achieve orgasm through intercourse. The main problem today is inhibited sexual desire. Many are just not interested and it's very difficult to deal with.'
One possible solution is the sensate focus method, devised by Masters and Johnson, the American pioneers of sex therapy. Couples are advised to refrain from intercourse for a while to take the pressure off the inhibited partner. Instead the method concentrates on sensual massage in the hope of reawakening desire.
'It can work,' said Dr Cole, 'but we've had nothing like the success rate that Masters and Johnson reported in the US. Quite often couples come to see us at the point where their relationship is breaking down and they can't even bear to touch each other.
'If it's not working we should be upfront about it. We have to point out that there is so much more to the relationship then sex. But if sex is so important to one partner or the other, then that's the end of the relationship and let's acknowledge it.'
Some women suffer from vaginismus, a painful condition in which the muscles of the vagina go into spasm. Raised awareness of child abuse has helped in its treatment. 'At one time, we just didn't think of asking about things like that,' Dr Cole admits.
If knowledge of human sexuality has increased, he has done more than most to spread it through his books and films. It is more than 20 years since the furore over Growing Up and he finds it depressing that sex education is falling victim to the demands of the national curriculum and the foibles of school governors.
In other respects, though, he is cheered by an openness in Britain today. 'You can go into WH Smith and buy The Lovers' Guide video off the shelf. I think that's wonderful.'
Not surprisingly, he feels that the permissive society that he helped to usher in has had more benefits than drawbacks. 'You can't compare decades in terms of human happiness, but in the area of sexual behaviour most men and women are more fulfilled than they were. On the debit side, there is a certain amount of sexual anarchy. And the breakdown of family life has offset the clear advantages.'
Does he have any regrets? 'If something seems like a good idea at the time, it's no good having regrets afterwards. My own belief is that I haven't done any harm. I have a file thick with letters from grateful clients. One woman even wanted to name her baby after me.'
Dr Cole has five children. The eldest is 36 and the youngest 14. His three marriages have all ended in divorce. 'I do regret that my own children have been brought up away from me,' he says.
Now four years from retirement, he lives alone with his books, his jungle of plants and his African fertility figures. 'I must be one of the oldest men in Britain still paying child maintenance,' he says with that smile which is never far from his lips.