http://www.armeg.com/Diamond_Grit_Ti...lls-A00074.asp

Armeg diamond core set in tiddly sizes, 6mm, 7mm, and 8mm, along with
the water adapter kit. The price would make your eyes water, but chris
onna bike, it's worth it. I spent 3 hours yesterday afternoon drilling
ten holes through 1/2" thick floor tiles (that had been used as wall
tiling) and the time included fitting the shower doors, etc.
In contrast, a fortnight ago I was unprepared and spent 4 hours drilling
6 holes and was utterly ****ed at the end of it, watching the bit like a
hawk and being very careful about position, speed, etc.

http://www.youtube.com/watch?v=7oh6xCKtdxA