If its only for a few holes then buy a cheap hss set (metal drills).
Use a masonary 1st to go as big as you can... even starting small and
going up (make sure not to use hammer action). The once you dont have a
masonary just go up in 1mm increments with the hss bits- it'll only
take a few minutes to get to 16mm. I tend to do this job after laying
the tiles but before grouting, leaving a few days for the adhesive to
set. Alternatively, go to a hire shop and hire a bit- you'll only pay
for the wear on it.
Calum Sabey
(NewArk Traditional Kitchens 01556 690544)