After a reasonable amount of experimenting and one entirely mangled bit, the following worked best to drill though what i can best describe as synthetic slate/stone tile ~12mm thick. (i.e. NOT a thin, glazed bathroom wall tile)
First - corded drill, non-hammer setting with a carbide tip, tile drill bit (looks like an arrowhead) to get a small ~3mm deep indentation in the tile surface. Reasonable pressure on the drill but make sure you cool the bit every 30 seconds or so. (i did this by dunking the tip into a tiny cup of water and it worked fine)
Once you've got a reasonable pilot hole/indentation, switch to a carbide tip masonry drill bit, on hammer action. Start very slowly and don't apply too much pressure early on or you risk cracking the tile. Keep the drill stable or have the bit go wandering across the tile.
Start with a small diameter hole. Widen once that's completed, using a masonry drill bit in NON hammer action.
I had 24 holes to drill in total - the first 2 took about 30 mins each using non-hammer action all the way with only tile bits and i ruined the first tile bit entirely.
Switching to the above method, i was getting each hole done in about 2 mins. No cracked tiles, no scratches on the surface and the new bits still look in good shape.
Loads of good answers above and i'm sure many folks with far more experience than myself will say never to use hammer action on tile of any sort.
Nonetheless, hopefully this helps someone else in the same situation as me who doesn't fancy spending an entire weekend drilling.