Since 1999, the number of temples to pampering has almost tripled worldwide, and the British spa industry alone is estimated to be worth around £2 billion.

These days, you wouldn't open a department store without a spa in it, let alone a hotel. Dentists, airports and hairdressers have them, too - and yet, despite their omnipresence, there are very few that I can wholeheartedly recommend.

The number of grand openings for spas and "wellness centres" that I have been invited to over the years runs into the hundreds.

You would be surprised at the number that are merely a room in a hotel with a massage bed and a CD of whale songs playing in the background.

There is, you see, no law on the definition of "spa" and you may commit to spending an awful lot of money before you feel duped.

So how do you know? Firstly, a proper spa should have an area in which to relax and have a cup of herbal tea before and after the treatment - so ask when you book.

A large number of treatment rooms and therapists is another clue to how serious the spa is. I have a natural mistrust of places that offer gimmicky treatments such as chocolate body-wraps or Christmas-pudding-themed foot rubs during December.

Espa, the British aromatherapy-based spa company, has bolt-holes all over the world and if a hotel says it has an Espa spa, you can guarantee it will be a proper, mother-ship establishment with plentiful, spacious treatment rooms, rigorously trained therapists and heavenly chill-out areas with saunas and steam baths for pre- and post-treatment.

Its signature Super Active Facial is 90 minutes of bliss (0845 6800 772; www.espaonline.com) and is tailored to suit your skin's specific requirements, whether you are crêpey, spotty or both.

This is one area in which celebrity endorsement has some meaning. If Gwyneth Paltrow is a regular at the Elemis day-spa (she is), you can bet it is one of the best in the country.

As well as the Mayfair haven (0870 410 42100), where you can hang out all day for lengthy treatments, Elemis has "spa pods" at John Lewis, Harvey Nichols, Debenhams and House of Fraser stores around the country for speedier indulgence.

The Power Booster Facial (£45; 0845 279 5005) transforms dull skin and relaxes the body in an impressive 30 minutes.

Cowshed Spas, despite the name, offer the last word in urban chic, with outposts in Notting Hill and New York. The original spa, a former cowshed at Babington House in Somerset, has had queues for its body and facial treatments for the past decade and is about to reopen after a mega-bucks revamp.

The manicures and pedicures here are the best you'll find anywhere. I have tried Cowshed mani-pedis (£40 for 45 minutes) in New York, London and Cornwall and all seem to withstand all manner of abuse - from sunbathing to washing-up.

Jo Malone treatment rooms offer pricey but reliable indulgence (from £65 for a 45-minute Express Facial; jomalone.co.uk). I always recommend them when asked "Where do I take my mum?". With the divinely scented ingredients and impeccably decorated rooms, they put the "treat" into treatment.

The one exception to my one- room "spa" rule is Crème de La Mer's treatment space at the Urban Retreat in Harrods. Since it is the only place in the world that offers procedures using this famously pricey product range, it is the most sought-after, one-room spa on the planet.