Between "R" & a RR sport, there are a different kettle of fish.
It all depends on your requirement really. One thing for sure the RR sport's running cost will be much higher & so is the petrol bill. Another factor to consider is the reliability issue. Don't think it can outlast the "R." To go for a SUV of this range, derv would be the way to go. These modern turbo diesel engines produce a tremendous amount of torque. Is torque you want in a SUV & not outright hp. Think Audi Q7 V12 twin turbo diesel model available on special order. Price is close to 95,000 quid. IMHO, I would compare an S3, Focus RS, BM 135i & 335i with the "R."