Can't say for certain if you'll find anything decent, but if you want to do some digging, the Vintage Threads Kilo Sale, which takes place this coming weekend in Manchester, could be for you.
Running over 4th and 5th September and taking place at the The Triangle Shopping Centre (Old Adidas Unit next to Tampopo), Exchange Square, Manchester, M4 3TR, it's vintage clothing by weight – grab clothing ranging from the 40s and the 80s, weigh it and you'll be charged £13 per kilo. Might be quantity over quality, but there's always a chance of something interesting sneaking through.
Times vary, with trade allowed in from 9-11 (Saturday) and 10-11 (Sunday), everyone else allowed in from 11am, with the event running until 5pm. If you want to register as trade, get in touch with the organisers.