I've been to loads sold at a few and you will get everything that you mention from rusty tat to the cream and stuff from all ages new race to pre war items are usually covered. Are they worth it in a word YES .
But be warned, if you go to sell, you'll be there early enough to see what everyone else has, and you'll come home with tons of stuff and sell 3 things yourself
(Voice of experience. Great fun though, if you don't take it too seriously)
From a cotter pin to vintage machine costing over a grand all under one roof .Half a day with like minded folk. Whats not to like . {apart from a cotter pin} .