Beyond a shimmering rainbow of satin ball gowns hanging from a rail, a flurry of activity involving hair rollers and brushes is taking place.

The air is heady with the sweet smell of hairspray as Anita Brown and her team at Neat Hair and Beauty in Knowle West get to work with combs, lipsticks and eye shadow to prepare teenage girls for their school prom.

By the time they step into their ball gowns, with their faces immaculately made up and their hair perfectly styled, they are almost unrecognisable from the girls who arrived barefaced wearing jeans and T-shirts.

It is as if someone has waved a magic wand. And in a way, a kind of magic has taken place in a modern Cinderella story, with a happy ending that includes donated spray tans, borrowed ball gowns, and classic cars chauffeured by well-wishers.

There are even a couple of real-life fairy godmothers, in the form of Heidi Wood and Jan Capel, the two women behind the Bristol Prom Project.

"We're doing it locally around Knowle West, Hartcliffe and Brislington this year, but next year we want to help girls all over Bristol go to their school proms," says Heidi.

The Bristol Prom Project was set up to enable Bristol teenagers to go in style to the American-style proms that have become a feature of school life nowadays, without having to cost their parents a fortune.

Heidi and Jan have a collection of 50 ball dresses that can be hired from £5 plus a £5 cleaning fee, plus evening shoes, costume jewellery, handbags, tiaras. And they organise spray tan sessions, hair styling, make-up, and even chauffeured vehicles.

Heidi, 38, of Kerry Road, Knowle West, came up with the idea after her 16-year-old daughter Poppy came home from school a couple of months ago, and told her there was going to be an end-of-term prom.

"She said a roadshow had come to the school with some beautiful dresses. There was a dress that she really liked, it was a raspberry colour. All her mates had been telling her: 'This is the one for you'. I asked her how much it cost, and she said it would be about £200, plus £25 for each alteration.

"I knew I couldn't afford that. I'd have loved to do it for Poppy, but I didn't want to get myself into debt. A friend was with me, and she said that she had a blue dress in a similar style that Poppy could have. She brought it round, and Poppy looked beautiful in it. It was a much better colour for her, and it fitted perfectly.

"It meant she could go to the prom, and I didn't have to worry about spending hundreds of pounds on a dress. I started thinking: 'If I can do this for Poppy, I can do it for other kids'."

Jan, 37, of Alison Avenue, Brislington, takes up the story: "We started talking about it, but I didn't think we'd have time to do it for this year."

Then something happened that gave the project an unexpected impetus. Donna Mitchell, a stunning 26-year-old who was well-known in Knowle West, died in a car crash in Bedminster in April.

Jan recalls: "Heidi knew Donna, and thought the prom project would be a good way of remembering her since she was so glamorous. She said: 'Let's do it – and let's do it in memory of Donna this year'. She was determined, so we decided to go ahead."

Heidi adds: "Donna was such a beautiful girl. I used to say she was the Brigitte Bardot of our day. All the profits made this year will go towards the fund for Donna's eight-year-old daughter Chloe."

This, then, was how the Bristol Prom Project began. But it could be said that the story of how the city's real-life Cinderellas have been helped to go to their school balls began many years earlier, at a time when Heidi's life was at its lowest point, and she had to put Poppy into voluntary foster care.

It was Jan who became Poppy's foster carer. And she not only looked after Poppy – she also became friends with Heidi, and in doing so has helped her to change her life.

While Heidi buzzes with energy, Jan is a calmer, more serene, presence. Yet behind Heidi's outward bravado, there is a vulnerability that becomes apparent as she talks about the events that resulted in her friendship with Jan.

"I was jailed for three and a half years for drug smuggling," she says. Her voice is flat and almost too matter of fact, as if this is something she has told people many times before, but still finds difficult to say.

Before Heidi begins to explain how she got involved in drug smuggling, the conversation moves on to problems she has been having with her hands and wrists.

Jan explains that Heidi has Carpal Tunnel Syndrome, in which the nerves in her wrists have been damaged, and that this may have been caused by the fact that she has Obsessive Compulsive Disorder (OCD).

"Heidi needs everything to be exactly in place. She will clean and clean things even though she knows she shouldn't because of her Carpal Tunnel Syndrome," she says.

So how did Heidi get involved in drug smuggling? She replies: "My mum died from lung cancer in 2003. She was only 56. I looked after her through her illness as her unpaid carer.

"To help me get over my mum's death, my dad paid for me and Poppy to go on holiday in 2004. We went to Jamaica and missed our flight home by about 10 minutes.

"I was standing in the airport wondering what to do next. It wasn't like being back in Britain where you can get a Yellow Pages and find a hotel nearby.

"I didn't have a clue what to do, and I started chatting to this bloke and was asking him about places to stay. Then he took mine and Poppy's passports out of my handbag.

"I just wanted to get home and I felt I couldn't mess with these people. I could have been shot – Poppy could have been hurt. I know I shouldn't have agreed to do it, but I still believe I tried to do the right thing as a mother."

Most people probably would not have got into such a situation. But Heidi, with her OCD and need to be in control of situations, is more vulnerable than most.

She looks so mortified about being in prison, that I remark that at least she was stopped at customs and didn't actually hurt anybody. Heidi is having none of it.

"But it would have hurt people if I'd got through. I had two kilos of cocaine strapped to my body," she says.

When I say that doesn't seem a very subtle method of drug smuggling, she says: "I was set up. I was a decoy. They were waiting for me as I went through customs."

While Heidi was in prison, her father died, and the childcare arrangements she had made with friends for Poppy had to be changed.

"I had to ask social services for help, but I told them I wasn't going to sign my child away to nobody, so they suggested voluntary foster care.

"I said I'd like Poppy to stay in Bristol. She'd already had so much disruption in her life.

"Jan became her foster carer. I'm glad in a way that I went to prison because otherwise I wouldn't have met Jan.

"This woman is amazing. She had my daughter to deal with, and her daughter was very ill. Jan had to go to Great Ormond Street Hospital in London every week, but she still came into my house every day to make sure everything was OK. I can't find the words to begin to thank her for all she's done."

Jan comes across as totally unflappable, and seems to have given Heidi the stability she needs. Meanwhile, the Bristol Prom Project has given Heidi a chance to do something positive, and has helped to boost her fragile self-esteem.

"I trained for so many things in prison like Reiki and Indian head massage, and hoped that when I came out I could find work, but as soon as the stigma of prison comes up then people don't want to know. I answer the question on the application form by saying 'will discuss at interview", but I never hear back," she says.

"I desperately want to get a job. I've been doing anything I can on a voluntary basis to try to prove myself."

It was while she was working at the Happy Landings pub in Knowle on a voluntary basis to get a reference last year that Heidi met Donna.

"We were doing Sunday dinners and Donna used to come in for dinner every week. She was someone you could drag through mud and she'd still look beautiful, but she was never vain and full of herself. She was really down to earth."

After Donna's death, Heidi and Jan began approaching friends and local businesses asking them to donate dresses and accessories for the Bristol Prom Project.

"I must have written to and emailed more than 40 bridal shops," says Jan. "Nicky from Class A Brides in Sandy Park Road was the only one who replied, and donated about 10 dresses.

"When we picked those dresses up, that was the first time I thought this might actually work.

"A lot of these girls have never been out of jeans and trainers, and it's a fantastic experience for them to get dressed up for a prom."

Nearby, real-life Cinderellas are getting ready to go to the Brislington Enterprise College prom at Jury's Hotel. The following night more girls will go to a prom for the Bridge Learning Campus in Hartcliffe.

And for Heidi, the unlikely fairy godmother who came up with the idea, the project is a chance to prove herself – and has also brought some unexpected magic into her life.

For more details go to www.bristolpromproject.co.uk.