granite tiles

i have instaled 12x12 granite tiles on my countertop in my kitchen, unfortunatly i have now got some slight lippage. ihave grouted the joints but wish to polish these edges down to a mirror finish i have access to grinders/linishers and i am familiar with using this type of tool please can you advise what and where i can get polishing discs/abrasive compounds and final glasing polish from. many thanks. Vin O'Leary. England.