You can't beat car boot sales as well,some of my better finds;Holosade "Hellhouse" and Desecration "Devils meat" on vinyl of some chap for a pound each,I got the original metal blade cd issue of "Show no mercy" of some charity stall on a car boot for fifty pence,but my best buy so far(not exactly thrash) Cathedral "Ethereal mirror" gatefold vinyl and "Forest of equilibrium" and a Prong vinyl of some woman,TWENTY PENCE EACH.
Recently got the Destructor reisue cd of ebay for one pence as well