well guys - thanks for all advice . . .
I got stuck straight into it on Friday morning - started the hole on the inside , got through the plaster and breeze block like it was butter . . but then damn pilot drill fell into the cavity between breeze block and brick! oops! tried to keep going without a pilot but after 20 mins of grinding away without a pilot I'd gone 5mm into the brick! luckily found a masonary bit I had kicking around that fitted the hole in core bit - a super long one - so went through brick from the inside then attacked it from the outside - by this point I think the core drill was blunt so had to put it on hammer to get through. . . .the guy in the hire shop had suggested I use hammer action!
so, got there in the end, hire shop didn't charge me for lost pilot or blunt core bit and gave me 20% of drill hire back for getting it back the same day
all in all not too bad, though I'm not exactly looking for opportuniteis to do it again . .
