Though it is possible to re-build them to a higher standard, from what I have heard the standard refurbishment attempts to bring the gearbox back to new specification. However, they are still used gearboxes that have previously failed and, from what I've managed to find out so far, they are more likely to fail again than any original unit
You are probably better off with a good, low mileage, used unit.

May '04 - Feb '07 R50, Feb '07 - May '10 R53. Enjoyed our time with MINI's, but ran out of space! Now Focus RS & Land Rover powered...