The circuit is still evolving. I have replaced the window relay and arranged to power the control circuit from both sides at once so that if one fuse blows, the other window will still operate. The relay is a fail safe so that if one window control relay welds in the on position, it will not flatten the battery.
The installation is complicated a little by this though. It is necessary to remove the relay socket from its bracket, take the front off it, remove the green wire with a ty rap to push down the latch and replace it with a twin wire before clipping the front back on, replacing the socket and plugging the relay back in. It isn't difficult but it is fiddly as access is pretty limited. The reason for this is my determination to avoid cutting any wires and to allow the car to be returned to originality if required. I have removed the fusebox and its bracket for access which I needed to do in order to find the best way to do the relay mod. Tomorrow I shall try to do the job whilst keeping it in situ. I think it is possible- I just need to make it easy!