One thing to be aware of is siting of the hole. You don't want to be close to a wall edge (at least a brick width away), and it would be worth taking into consideration any loading on the wall which you are going to take a chunk out of. For most situations the latter won't be a problem, but as you'll be removing the equivalent of a brick from the wall it might be.
Diamond cores break out cleanly on the far side of the hole, whereas TCT cores smash their way out leaving a mess behind.
And as for buying a drill - an SDS from Homebase or wherever will cost less than 50 quid. It'll be good enough for these holes.
Andrew