Again, thanks guys for all your support. It really does mean a lot.
The only gearbox I found online with the same PIR code as mine is
this one for £3079.
It's from a car that's done enough mileage (86k) for it to need a service too. Also, the seller's feedback has a few people complaining about late deliveries and non-working parts, so I'm not sure they're tested before they're sold. I also think it's horribly expensive for a used part, considering the tiny target audience.
Other than having (yet another) four-figure bill, my worry is that as soon as it gets fixed, something else is going to go. Mackie told me the reason it's so expensive to replace is because the whole front end of the car has to come out, engine included, to fit a new gearbox. If that's the case, I may as well get a new power steering pump & aux belt fitted at the same time. I'm still not happy with my steering and the lack of feedback through the wheel makes me think it's on it's way out.
Where does it end? (other than a trip to webuyanycar.com)