Hi Duncan
Welcome back, I'm similar, been back about 3 years now : )
There's a whole other thread on the new car/transmission here:
http://www.oople.com/forums/showthread.php?t=178454
They haven't officially confirmed what it is yet...IE, just new gearbox, or whole new car. It's looking like a new car to me from the images, but maybe some crossover of parts.
If it works/fits existing chassis it will need drilling for new mounting points...other than that not sure.
I run the B5m; it's pretty much bomb proof. Personally I'd give it a fortnight, see what AE are up to. If it's a new car with some crossover spares, why not grab that for yourself and give the boy the B5m?
HTH!