I've been speaking to my brother Richard (whom some of you will have met), who knows quite a bit about cars. It seems that his son's garage have someone in Plymouth who rebuilds gearboxes for them, for a very much more sensible price.
So on Monday I'm taking the car down to Devon and leaving it in Richard's care. They'll take the gearbox out of the car, send it down to their man in Plymouth who will rebuild it and send it back, and then they'll re-fit it into my car. All this for just a touch under a grand.
Watch this space for further news.