The place I work at produces a glass polish by the name of tecepol - this is basically cerium oxide. I asked guy who produces it about particle size and he reckons less than 1 micron. Think I've got about 400- 500 grams. If anyone fancies trying to see if its any good post below. If there's a lot of interest I might put a few packages together and ask folks to take 1 and post the rest on i.e saving me posting it all separate. It would be nice if people could feedback on results too.