I haven't found a decent training course in the UK for this, there are a few but i don't agree with the way they polish there stone, crystallization as it blocks the pours in the stone so it cant breathe causing problems. The best place to learn is in America if you are really serious about it, i have just learnt myself as i lay natural stone floors i have had chance to experiment and teach myself, also i work closely with a diamond polishing manufacturer and i try new a different products for them. The set up cost would be around £10,000 to get all machines, diamonds etc. There is a guy in the midlands that i know who does diamond polishing and he was talking about doing some training this year, he is very skilled at this buisness, he has worked and trained in Spain, Italy, and America. If he decides to run a training course i will let you know.