I've just got back from picking the car up. It's like a totally different car.
The movement in the gear stick I had in 1st and 2nd has gone, and it's a lot smoother going into gear.
My wallet is now £1k lighter. They showed me some of the old bearings, and they are also sending me some pictures what they took that show the pitting and the wear to the bearings. In one of the pictures, you can also see where some of the teeth on 5th have been worn away on the edge!