The brochure is one of those thick, glossy affairs with cleverly lit photos of sunshine glinting on water, robes casually flung over poolside beds, a huge glass vase filled with flowers.

Beautiful yet approachable men and women in white coats smile welcomingly on the pages. All have perfectly plucked and arched eyebrows.

Some raise their heads as their bronzed backs are massaged; others snake strong arms around a recumbent swimmer as they glide them backwards in an effortless lap of the large, sun-filled pool room. They are the "come-on" for a spa, the lure for those who wish to part with large sums of money in a doomed-to-failure bid to become part of their glowing, cleansed club.

How often have I been seduced in the past by such siren calls of guaranteed bliss, handing over obscene sums for a day in a hotel spa or an optimistic annual fee for the newest gym in town? One year I calculated I had paid £1200 for an hour-long stuttered crawl, jostled and splashed by other suckers getting their money's worth.

Let's not even mention the branded garments and special trainers bought to complete the intention to redefine and recreate an unwilling body. Usually after one miserable visit they joined the aerobics gear, the tennis and squash dresses, the yoga pants, the day-glo wrap-around ballet shrugs (for that vital cooling-down period) and all the other once-worn items in the cupboard tomb of failed intentions.

And yet, here I am: swimsuit rolled in a towel carried in a plastic Le Clerc bag, entering the swish 18th-century thermal spa in Lecture, a fortified walled town dominating the countryside in the Gers.

In the afternoon heat, the elegant full-height windows of the imposing stone mansion are opened onto a wrought-iron balcony overlooking the walled courtyard. Embedded lights dramatise the facade at twilight. It is everybody's fantasy of south-west France. Even the bees hum in tune.

H and I climb the broad stone steps to the first floor and a desk manned by welcoming receptionists. The odd white-coated attendant drifts past, all young and pretty with perfect eyebrows, of course. I am currently obsessed with eyebrows.

It is my first visit but not H's so I already know I will not need to hock the silver for entry into this luxurious domain. I won't even have to promise undying, blood brother fealty to secure a monthly payment contract. Instead I pay less than £8 for afternoon entry into a marbled sanctuary with pool, sauna, hammam (Turkish bath) and Jacuzzi. Changing is done in individual tiled and seated cubicles, not the fumbling embarrassment of locker rooms with puddled floors.

There are only four other people in the pool who politely turn the other way as I splutter my way through H's aqua aerobics orders. The water temperature is a glorious 28C. I am in heaven.

French heaven. For this is no ordinary spa. On the floor above us is another similar pool, augmented by treatment rooms, massage showers, assessment offices. The equipment around the pool is medical - lifts to gently lower the disabled, grabs and seats to secure their confidence, buoyancy aids stacked in teak boxes.

Without exception, the users of this floor are here on prescription from their doctors, as are the many treated in more than 100 designated privately run spas dotted around France. Yes, you may need to read that again to believe it.

Spa "cures" cover numerous ailments from skin diseases to arthritic complaints, with a host of muscular, respiratory and circulation problems in between. There is even a weight-reducing programme.

Doctors prescribe a block 18 days. The spa can be local, miles away in the Alps or by the sea, depending on the specific need. Travel, hotel and meals are 60-70 per cent covered by our health cards. Top-up insurance normally covers the rest. Your husband/partner/whatever can come too, paying just a tiny amount for the shared hotel room and food.

Many professionals are now admitting that it is little wonder our envied health care system is going broke. It exceeds its budget by billions of euros every year but no government is prepared to tackle the problem in any meaningful way.

The French expect and demand such excellence as a right and frankly they (and me, as I'm working) pay through the nose for it in punitive social charges that eat up a huge percentage of the monthly pay.

Taxis to and from appointments, homeopathic remedies, support stockings and the like are all a part of the service; a service the French will not, at any cost, give up without national disobedience.

Leaving the Lecture spa clutching the shiny brochure for further reading, I start to plan a little holiday "taking the waters". Should I go to the Alps to help my ashtray lungs? Perhaps the seaside for the spots of psoriasis on my elbows? Maybe the Loire for my calf cramps?

Shockingly, I feel no shame at my thoughts. I'm shocked I feel no shock. Has my inner "because I'm worth it" Frenchwoman been unleashed? What next? Perfect, arched eyebrows?