Sorry for the tardy response. Yes - the holes / plugs in the rear bumper were completed in the factory.
Total cost (from memory):
Bike Rack Prep - £70
Bike Rack - £350
TOTAL - £420 (incl VAT)
Expensive, but quite a bit cheaper than the tow bar option.
Having used the rack extensively over the past few months taking it up the Peak District and the North York Moors, I can report that it is a very stable and well designed piece of kit!