I finally refitted the cleaned out Oil Tank, Sump, Oil Pump and all oil pipes today. I fitted new Balls and Springs in the Pump (thank you Peter Kemp), checked Pump action as per book, refilled the Oil Tank with Castrol GP50 after first bleeding oil down the feed line before bolting up the Pump. A cupful of Oil injected over the Exhaust Rockers and 30 mins to allow the oil to drain down. Refitted the chain cover.
I started the engine and observed the return pipe in tank. For the first 30-45 seconds practically nothing (I was getting just a little concerned), only the occasional, merest hint of a sputter of oil, and then suddenly after about a minute, the oil started to flow first a trickle and then a continuous stream of oil and air sufficient to show as tiny bubbles on the surface level of the oil tank.
Now for a run out tomorrow and then on to the dynamo charging (or lack of).
Thank you all, for your help and advice.
Mike