If the main bearing needs to be replaced then that's nearly £500 alone, then you have the cost of the selector forks, the other bearings, various seals, bork rings....the list goes on. It's a good £1100 in parts alone plus the cost of the gear set and the labour to build and shim up a uprated box!
Then you have the cost of taking out the engine to fit the new "uprated" box.......
IMO, £2700 is cheap for a brand new unused uprated box.
This is not aimed at anyone, just giving my opinion on the subject.
Where? Find me one and i'll buy it for the box and flog the car one. If you do find me one make sure the box is not fooked! Just because it's got a Quaife box in it, it does not mean the box is in good condition.....