Hi,
The latest:
I contacted Dennis Altman of Rover Ronovations. Very helpful. Ex-USA submariner in pneumatics. He said it was possible the NRVs. So after taking the valve block assembly out three times and checking the work I hd done, Lurch, the garage queen now sits up after 30sec - 2min and seems fine after that. It does lose about 6cm overnight, so I haven't found the leak, yet, but the car bimbles along happily once it's up and the pump cuts out some of the time, so it's not getting too hot. (No it's not the thermal cut-out). As q-rover says, it's not too demanding a job. A 12mm open spanner, an allen key and an 8mm and 13mm socket is all you need. Oh and a posidrive. Quite enjoyable really. Don't go to Rover! If I can do it, you can do it.
Good luck.