A boot fayre (or "car boot sale" if you're boring) is where a bunch of people drive their cars into a field, set up tables and/or blankets, then cover them in a bunch of shit they don't want any more and try to sell it for a dollar or two.
I was at one the other day and one of the stalls had an actual pick axe, which I was very tempted by, but I didn't want to have to carry it back and didn't want to attempt to explain Minecraft to my family nor any police who would have inevitably pulled me over and searched my car. :C