Sounds like you and I have had similar issues Sam...I had a circlip wander down the output shaft and the box tried to be in 3rd 4th and 5th all at once. I've got the box back together but i'm a little while away from getting back on the road - and now I'm nervous!
Also, is it weird for 2 blokes to publish that they've had similar problems with a tranny?
Good luck with round 2 rebuild