MOST of us women think we know our own body and shape. After all we know our weight down to the last pound, our dress size, height and shoe size but when it comes to our bust a staggering 75 per cent of us are wearing the wrong size bra.

Jacqui Smith, who is 44, an admin officer and mother of four, says: "I always thought I knew my size and was wearing the right size bra. I can't believe I've been wrong for the past 15 years."

Revelation came when Jacqui agreed to be measured and fitted at Contessa, the lingerie specialist in High Wycombe.

Contessa's manageress and trained fitter Linda Quincey measured Jacqui and told her the bra she was wearing wasn't doing her any favours. It was too tight and the cup too small, making her look and no doubt feel cramped. Instead of a 38C, she should be wearing a 38E.

Once in the right bra, the difference was immediately noticeable, Jacqui said. "It is so comfortable, I can't believe the difference. I realise my shoulders aren't being dragged down and it looks so much better."

So why had she put up with the wrong size bra for so long?

"I suppose as I put on a little weight, subconsciously I thought a tight garment would make me look smaller.

"But the biggest reason I've never had a fitting is that I imagined I'd have to undress before a stranger and it would be embarrassing."

She was pleasantly surprised. Linda took the measurement around her midriff the underband area while she was still wearing her bra. You can even keep your jumper on if you wish.

Then each time she brought Jacqui a bra to try, she discreetly closed the curtain while Jacqui changed, then asked if she was ready for her to enter so that she could check its fit.

"I certainly wouldn't hesitate to come again now I know it's this easy," Jacqui added. "There's just one problem. Now I want to change all my bras for the right fitting ones."

Osteopath Diane Kheir, from High Wycombe, explains that wearing the wrong size bra can affect your posture, give you tension and lead to medical conditions.

She said: "With heavy busted women the shoulders tend to carry the weight of the breast and wearing the wrong size bra can cause pains in the shoulder, neck and cause tension headaches.

"If the bra restricts your rib movement this can exasperate a pre-existing condition like asthma, a lung condition or give you indigestion."

The choice of bras at Contessa is vast. There are bras that promise uplift, support while playing sport, comfort, cleavage, a bigger profile or a more modest shape whatever you want, there's probably a bra that will do it.

Which is just as well as women came in so many shapes and sizes obviously but also with very personal requirements.

Linda says: "Some ladies like to feel strangled by their bra and wear them really tight, others like a crop top style that they can hardly feel they are wearing."

Some women even need two different sizes, as they change shape depending on the time of the month.

Nicky Peng, a Chinese student studying Business Information Technology at the Buckinghamshire Chilterns University College, had a quite different problem. She is very petite and finds it hard to get a bra that fits well and looks good. Bras start at 28 AA, but there is less choice in smaller sizes.

Nicky balked at some of the bras on offer, like the one filled with an amazing soft and pliable gel. In the end, after trying on most styles on offer, she settled on a Wonderbra that looked gorgeous.

After watching these two go through their paces I guessed I'd better have a go. And yes, I too was wearing the wrong size. "The back of the bra is riding up your back which shows it's the wrong size," Linda pointed out. "It should be straight across."

She suggested some styles to try, several of them with underwiring. I'd not worn a wired bra since one I'd tried donkeys years ago which was most uncomfortable. Now most styles come this way, Linda says, but they are far more comfortable than in the past. She gave me several to try and I chose a Pretty Polly model.

Linda likes to find out the kind of look people are after. If you feel larger than you'd like, wearing the correct style can make you look smaller. Seamfree bras are particularly good.

Then people sometimes want a style for a particular outfit. A bit of pushup can work wonders with an evening dress. But with a T-shirt, a smooth seamfree look is ideal.

People often get confused about size. If you put on weight you may decide to replace, say, a 34B with a 36B. But a better fit might come from a 34D or DD. Hence the need for expert advice, which is free.

Linda even had one customer who ended up crying in the changing room when she was helped to find the right fitting bra. She told Linda: "To think I could have looked like this all those years."