After a day of checking I found the cause of my screen remaining blank or flicking On intermittently, down to a corroded and chaffed wire ( white / red stripe Wire ) Down at the bottom of the centre console , heater metal frame (see pic- green circle)

After a soldered repair it came straight back to life, however it has now highlight I have a further electrical gremlin, around the Sat nav drive box, which I am yet to resolve, it occosionally works, so back to wiring again.

But at least I have a screen ,radio, tape and cd drive on

Also in relation to JB tourer having his joint of wires underneath the driver seat, mine did not. I found them (purple /pink ) all soldered together behind the centre console along with a bunch black wires, so assuming as my car is a mk2 it may have been a modification by Rover on the later cars. See pic - red circle

I hope this may help someone with a similar problem in the future

Sat Nav issue resolved, turned out to be the corroded 6 pin cable inside the Sat Nav Drive as well documented on the forum