Probably the best you can buy are Armeg PTC - A Starter kit will set you back around £200. - this will get you a few guide drill bits 6mm & 8mm and also a couple of crowns for the 2 standard sizes of shower pipes - also a water feed atattchment & water pump bottle. These are absoultely the best on the market and are guaranteed for 100's of holes into porcelain - then when done for porcelain will last forever on ceramics.
The gamble is - you could spend around £100 on a set for ceramics - I have a decent Rubi one - but then you are snookered when you need to drill porcelain.
The way to get you money back is to charge £10 or so per hole for the porcelain -
It may be worthwhile looking on e-bay for the Armeg sets - there is a shop selling them - you could probably get a better kit for a fraction of the price.
Have a look at
Armeg PTC Porcelain Tile Cutter for the range
I like buying toys that make my life easier - SAVE TIME & MAKE MONEY
Also have one of these - Senco Duraspin DS275 18 VOLT Collated screw gun - not cheap at around £300 - but my oh my does it fire in those screws fast, when over-boarding floors. Again I still charge the going rate for over-boarding , but it takes a fraction of the time. Have made my money back easily
P.S
iF YOU JUST WANT A COUPLE OR SO DRILLS FOR CERAMIC TILES - AGAIN SPEAK TO DAVID AT TRADE
TILER - THINK HE SELLS THE RUBI ONES A SEPERATES