The last of my components came today so I put the floor, the mats and the seats back in. I've just tried it on the road (rather than just trundling up and down the yard) and all seems well. The gearchange is still a bit stiff but once again it's probably due to the box being very new and tight. Finding third gear is a bit of a fine art, but I think I've got the hang of it now, by holding the gear knob delicately between finger and thumb and pushing slightly to the right as well as forwards and it'll go in. Maybe I could refine it by tinkering with the various stops and springs, but it will do for now. So that all works well and I've not heard the whine of a loose gearbox on the overrun either, which is what this gearbox swap operation was all about. Success.