There ARE other brakes you can stick in the R.
Changing all the calipers etc?
There is very little options for discs. £700 for Godspeed discs, £1150 for Tarox and £1200 for genuine discs.
The avoidable big bill is to get the brake calipers rebuilt after the first set of brake pads. Don't ever push the pistons back into the caliper.