West Midlands Police sell unclaimed bikes through auctions. They typically go for around £20-£40 for a lot of 10 (http://www.astonsauctioneers.co.uk/west_midlands_police_auction_catalogue.html). I suspect most of them end up on Gumtree at that price each.
Thanks for the link, It would cost me quite a bit in petrol to get up there to pick the bikes up though...
I have refurbed a few bikes from 1990s road bikes to a cheap Apollo hybrid. Never made a cent on them. I have made money buying nearly new stuff at cheap prices then selling them on. It's not easy and items don't come up too often. you have to search all the ad sites as well as local supermarket boards etc...
If you do want to have a go only buy quality stuff. At least Reynolds 531 or Columbus Aelle, try and get Reynols 653, 753, 708 make sure the wheels are in good order otherwise you've spent £50-100 already. Most of the ebay stuff is junk, one old Reynolds 753 bike sold last week for £330 so you're going to struggle. A cheapo £200 Viking road bike will be lighter than most old 80s and 90s bikes and have more gears and be guaranteed for at least a year. Decathlon do a full STi equpped alu-carbon bike for £300
I know, I have one! Thats what is putting me off, someone cam buy a new bike for £300 then why buy my seconds? I think Yello is right, I am going to need an angle.