Mr ZZR1200 popped round this AM as arranged (Thank You for your time and P38 knowledge that you shared) , before he arrived i had the engine warmed up so he could see the hot at the top and cold at the bottom phenomenom.
As said, on arrival the radiator was hot at the top and cold at the bottom-we discussed what i had done, what i had changed and what results i had seen. I showed him the mangled open thermostat which was to be my next step to confirm circulation/flow through the radiator. Before i fitted this Mr ZZR1200 set up his pressure test equipment and proceeded to pressurise the system and check for leaks etc. - conclusion was that there was a miniscule drop and not sufficient enough to cause the overheating. In the end we agreed, after a lot of deliberating that we had to fit the mangled open thermostat before going any further.
This afternoon, changed the thermostat and filled her up really trying to remove all air locks by filling radiator. top hose and matrix separately - warmed her up on the driveway - the radiator as i hoped did get hot all over - this meant that the circulation problem was to do with the thermostat not opening - yes the thermostat that i had already changed twice.
Took her out on a test run and apart from the temp needle indicating a lower temperature than normal, everything was ok - managed 20 miles with absolutely no problems at all (before i could only do a couple of miles before she overheated) the only other thought from MrZZR1200 was that the expansion tank cap was faulty ie allowing pressure to be expelled thus not allowing the system to get hot enough to open the thermostat.
Suggestion now is to get a new thermostat and expansion tank cap - i will fit them next weekend and Mr ZZR1200 is going to pop round and look at the radiator/thermostat etc through his heat camera and see if it working as it should.
Once again, thanks Mr ZZR1200 for your time and knowledge in helping me resolve this problem.