I noticed that arceuro have these in their clearance section, £4 each or a set of 6 different gradesfor £20. I have the green and grey ones of these, usually used for concrete finishing but what I do is use them for putting a quick grain on ally and finishing edges of machined parts by hand. They are great, and at that price I would certainly reccomend them, they work great on alloy and steel and last a long time.
Here is a motor mount plate I made this last weekend. It really was scratched to buggery but a couple of minutes with one of these pads made it half-presentable. You have to look past the dirty fingerprints