They look like brown string vests draped across a hill. Dry ski slopes across the country have given novices the chance to master the snowplough before making for the mountains.

But today, such facilities have to compete with “real snow” as indoor centres open across the UK. One such place is “a giant fridge-freezer in the middle of Yorkshire”, which is how Anderson Garland describes his place of work near Leeds. He is head of the ski and board school at Xscape Castleford, where the 190- metre long, 37.5-metre wide indoor ski slope is covered in about 1,500 tonnes of “real” snow.

Michael Sutton, in charge of sport and PE at Ackworth School (in the 1960s, one of the first schools to take its pupils on an annual ski trip), took more than 50 children on several trips to Castleford last October for skiing and snowboarding. “I will not be going back to plastic,” he says.

This veteran of more than 20 annual school ski trips has used the dry ski slopes at Rossendale, Sheffield and Halifax in the past with great success and found them cost-effective in eliminating what he calls “beginner antics” once abroad. But the “positive transfer” of skills he found when the school went to Lake Tahoe at Christmas has convinced him there’s no going back.

He praises the standard of tuition and the quality of equipment at Xscape.

Thumps and bumps are less hard indoors too. “When you fall it’s more of a cushioned landing,” he says.

Mr Garland says that children find learning easier on man-made snow than on dry ski slopes. Your class won’t have a true snowflake moment, since technically the man-made snow is composed of ice crystals. Not that you can tell.

The SnowDome at Tamworth in Staffordshire uses a different kind of snowmaking technology, but the chief instructor there, Chris Webb, is not allowed to explain it to outsiders. It runs two academies for beginners under the main 170-metre long, 3-metre wide slope. Since it opened in October 2003, more than 200 schools from Liverpool, Cumbria, Lincolnshire, Scotland and Yorkshire have brought their pupils for lessons.

Mr Webb is aware of the drawbacks of artificial slopes. “You can get friction burns when you hit the ground, tear your clothes or cut your skin; people used to get ‘skier’s thumb’, injuring themselves by trapping a digit in a hole in the slope when they fell, and, because Dendix provides greater friction than real snow, people go more slowly. They gain confidence, but it’s misplaced because when they get on the mountain they go faster than they’re used to.”

However, injuries are extremely rare. There are no official statistics comparing different surfaces, but skiing in general has become much safer because of improved equipment. Betony Garner of the Ski Club of Great Britain reckons: “There are fewer injuries on an indoor slope with snow.

The indoor slopes are newer than most of the outdoor artificial slopes so their facilities are more up-to-date. The downside is that they get very busy, so it’s best to go off-peak.”

There is an indoor ski centre in Britain that does not use man-made snow.

The three slopes at Calshot Activity Centre, near Southampton, are covered in Snowflex, used by the newer outdoor artificial ski slopes.

For Mr Exall, a former chairman of the English Ski Council, snow is best.

“Man-made snow in an indoor centre helps beginners learn to ski in a controlled environment, unlike on a mountain where conditions change from minute to minute. On an indoor ski slope, the designers can create an ideal area for learning to ski.”

Xscape has started building its third centre, at Braehead in Scotland, expected to open in May 2006, while Godfrey Spanner, the man who devised Thorpe Park, is awaiting planning permission for SnOasis, a pound;300-million development at Great Blakenham in Suffolk,providing a 100-metre high, 500-metre long piste in a year-round winter sports resort. It is scheduled to open in 2007.

ALL THE DOPE YOU NEED ON THE SLOPES

SnowDome, Tamworth Tel: 01827 308410; www.snowdome.co.uk; schools@snowdome.co.uk. Lessons from April to November, pound;75 per group of 12; December to March, pound;110Xscape Milton Keynes Tel: 01908 680826824; events@xcape.co.uk; www.xscape.co.uk. Tuition from pound;10Xscape CastlefordTel: 01977 523091; www.xscape.co.uk;

michael.beadle@xscape.co.uk. Groups of 10, 9am and 6pm, Mon- Fri, pound;150 per hour (including equipment)Calshot Activities Centre Tel 023 8088 4913 (bookings); 023 8089 2077 (enqs). www.calshot.com;

calshot.ac@hants.gov.uk. Prices: pound;44 to pound;88 per 90-minute session for group of 10SnOasis: www.snoasis.co.uk