Phil,
The Carphone warehouse kit does not require drilling. _ it's actaully a Nokia kit.
There is an adapter kit which I forgot. I think it was £15. It is attached to the console to the left of the radio using double sided tape, then the phone holder screws to that. It comes off clean as I recently removed one from an S3.
All cables route with no drilling, and the main control box sits in the well under the passenger foot space. btw, if you haven't looked, lift all the carpets on the passenger side and remove the cover that is exposed. I think the ECU is in there; there's plenty of space for the phone control box.
The radio harness is a worthwhile addition, as then the speaker pod which comes with the Nokia kit is not required - all sounds come through the radio speakers.
It works really well. I tried headsets, but much prefer this option.
MartinW - Dolphin Grey 1.4SE