In message , Ron Lowe
writes

There are things designed for the job...
I used these:

http://www.cablecraft.co.uk/ProductGrp/0004000c

Drill a 6mm hole with an SDS, ( Granite here too, Aberdeen ) hammer one
of these in, and tie the cables to it. Job done.

Excellent - thank you. Yes, that is what I have ordered. I'm about 45
miles west of you, and delighted to hear that an SDS drill will make a
hole in granite!
--
Graeme