eBay and Craigslist finds

Although it's been done nicely enough, it's nothing special and having reached £82 without reaching the reserve, I'd be looking elsewhere.

Conversions tend to be overpriced, being as they are fashionable.

I've bought complete, roadworthy, mid/late-Eighties Peugeots and Raleighs of Ebay for +/-£60: wait for local bikes that the seller won't post as this depresses the price.

This. Retrobike has a list of people that will collect bikes for you, I've used two of them recently without issue. One of them charged petrol, the other didn't ask for anything (I just arranged courier).

531 frames are ten-a-penny, eBay is sometimes cheap but try other forums like I mentioned above as ctc/retrobike often has decent stuff for cheap.