You & I sound very similar.I used to go a lot,but don't get the time now.One of my best bargains was a Victorian slate fire surround for £10.
Have you tried farm sales?I go to them quite often.The furniture is a lot cheaper than normal auctions because most of the people there are farmers & only want agricultural stuff.I got a lovely old dressing table for £25 at one a couple of years ago.
My mil bought a "lot" of costume jewelry at auction, filthy manky stuff. Paid £11 for the lot. Cleaned it up in her proper cleaning machine and discovered a diamond ring worth £500+
Now why doesn't that happen to me?