Nice one Rich... Best of luck. 
Thanks Shaun.
Cooling system back together this afternoon so I decided, before start up, to use this pressure test kit that Corin lent me:-

So found the correct adapter for the VR6:-

........and started pumping:-

Got it up to 15psi:-

........and the pressure was dropping quite quickly

I had a look around and found two leaks, one from the thermostat housing and one from the drain plug in the transfer tube.
Took the radiator panel back off, thermostat housing back off and fixed the leaks.
Re-pressurised and this time, much better. Just a couple of smaller leaks from two hose connections.
Replaced the jubilee clips and its now holding 15psi for at least 5 minutes

My optimism is rising

I'm now going to turn the engine over by hand, just in case the head gasket has gone and water has been pushed into a cylinder.......don't want the engine to hydraulic!
Then its fit the battery and give it a go.........back soon............