Hi Bernie
Sounds like a new rad job to me - or a head gasket (or both). I'd get the flow rate of the existing rad checked. The cooling system is marginal at best, so it's always a good policy to have a new High Efficency Radiator fitted. Do compression test on the cylinders to see if there is any leakage, check for bubbles at the rad cap when running etc.
You need to speak to Uncle Malcolm in Somerset.