I'm in Devon so not far from Col-pax who have been mentioned in other threads on here.
The engine and gearbox are out of the car already so easy enough to take the box to a specialist for a once-over
I'll probably pull the valve body tomorrow and see how much more I can get out.
That said, I've seen a few comments from people in the US who just run Dexron III in them as a matter of course, so maybe a few hundred miles on it won't have affected it. Fingers crossed!