I finally got the Gun to work properly. Looking at the diagram sve1976 posted I couldn't work out why my microswitch was on the other side of the unit. Then I twigged, after watching a video on how to rewire the gun mechanism. I didn't have the limit switch! I think it was originally delivered with the kit but not fitted - it was included as part of the enormous wiring loom that came with the kit. I had to root around in the tank junk box to find it. After that, as soon as I realised that the motors switch on the negative side, and more fundamentally that the "0V" line from the microswitch needs a permanent nought Volt connection, everything worked.
Inside the top of the gun - the long black wire is the 0V connection to the main power line to the battery. The "turret" connector has, from left to right, plugs for lights, gun elevation and firing (one power and a signal line for each) and for the gun traverse (ex turret rotation) Everything got moved a couple of times, I made a nice neat installation and then found that the body top wouldn't fit....it all goes in now!





Switch access throught the engine hatch



And I've started on the exterior bits and pieces: Spare track/extra armour, and the gunsight. This is fixed to the top of the recoil unit so it moves with gun traverse, and so does the sliding cover plate.