Having the system cleaned out with the aid of a compressor, has fixed the problem. This is done by a water hose and the air hose connected before the end of the water hose. There is a 3 way tap at the end of the hose - 1 water, 2 air & 3 none-off.
Unfortunatley, I wasn't told that I'd come out of the excercise ringing wet! :)
The hose was connected to the bottom radiator hose, (the top radiator hose disconnected also)and putting my hand over the top radiator outlet to prevent water from coming out, from the water being filled via the bottom of radiator hose, the radiator is filled right up. A 'shot' of air is let into the radiator which the water spurts sky high ...and all the gunk as well. What goes up, must come down, in my case the water being literally 'bucked down on top of me'.
The place we undertook this was 14 miles from my house. We transported the Chev by car trailer to the place, and I drove it home - 1st maiden voyage. Never boiled once. Yahooo!!