1960s Speed Twin

Chap local to me has a 1960s speed twin in his garage. Last year, he was looking for £3000 for it and it didn't sell. He know thinks it's worth £4000 and it still hasn't sold! I've looked on ebay etc. and prices seem all over the place. I'm quite keen as a project and don't want to stripe him up (he's not stupid though). Any ideas what it would be worth if running and done up (I don't mean concours, but just tidied up, chrome cleaned that sort of thing)?