The high street is having. a facelift. In an unprecedented flurry of activity, new retailing concepts are being launched, while some of the 'oldies' are being revitalised. Marks and Spencer is testing new layouts, shops within shops, satellite stores. The experimental Woolworth stores are light years away from the traditional Woolies. Burton has begun a blitz to install some of its high street names in branches of the department store chain Debenhams, which it has just acquired - with the controversial 'galleria' concept to follow.