Thomastik Visions going for £12 or so per set on ebay. They're old stock, but sealed and unused and seem perfectly fine in every way. Seller is based in Hong Kong, but offers free postage. I've ordered from him a couple of times and the strings come in about 7-10 days. Nice strings. The "heavy" gauge are best: they seem very, very similar to the new Vision Solo strings that are retailing for £40+ at the moment.