A South Yorkshire children's clothes range is proving so popular on the mountains and the high street it's selling out before it's even got to the shops.

Spotty Otter, which makes children's outdoor gear, doubled its order to manufacturers for this year's winter stock after high demand during last year's cold spell and has added eco-socks to the range. But even that may not be enough as pre-orders come flooding in.

Director Stephanie Jones said they had to order most of the clothes six to nine months in advance, so it was difficult to predict demand. The Spotty Otter range is sold in about 70 outlets from Aviemore in Scotland down to Cornwall. It is also exported to Poland and the Czech Republic, with deliveries soon starting to Denmark and the Netherlands and interest from Russia.

The company, based near Penistone, also sells the range, and other children's outdoor clothes, at its sister firm Little Trekkers' two shops.

Stephanie said: "We've been told by our retailers that Spotty Otter is almost like a cult brand. If somebody walks up Snowdon with the kids our clothes will be able to cope with the conditions, but our down jackets are also apparently the thing to wear on Islington High Street."

The company, based at Bullhouse Mill, Millhouse Green, is being helped by Enterprising Barnsley, with marketing and general business advice. The Enterprising Barnsley programme offers business support to Barnsley businesses with growth potential and has helped create more than 600 jobs in the borough.

"The coaches from Enterprising Barnsley are great to talk through any plans we have got and point us in the right direction and they have also been great at helping us with things like social media," said Stephanie.

This winter Spotty Otter has added extra warm socks, made of a mixture of bamboo yarn and Merino wool, to its range and they too are proving a hit with mums and dads.

And it's not just ordinary mum and dads that like the brand. Celebrities too have been snapping up Spotty Otter clothes. But Stephanie is keeping mum over who.

"We have taken phone calls from well known people buying for their children, but it wouldn't be fair to say who. Customers are prepared to travel some distance to get their hands on some Spotty Otter gear.  We had someone drive all the way down from Edinburgh to the Little Trekkers' store at Elsecar Heritage Centre just to stock up on Spotty Otter items."

The range includes waterproofs, down jackets, fleeces, boots, mittens and UV protected clothing for children from babies to ten-year-olds.

Stephanie, a former midwife, and her husband Matthew, an IT expert, set up Spotty Otter in 2007. In 2000 they had set up Little Trekkers as an on-line shop selling children's outdoor gear. They later opened a Little Trekkers shop at their Bullhouse Mill base and this autumn another at Elsecar Heritage Centre.

Now the pair are just waiting for the winter to really bite so that sales go up even more.

"We are still waiting for the really bad weather to kick in. The last two winters might have been tough, but they've been a real boost to our business," said Stephanie. "Last year pre-orders meant that with some ranges we had sold out before the stock got off the ship and this year again we are already heading that way."