this turned out well. I cleaned the oil pick-up which was plugged solid, then replaced the cam-chain tensioner which was toast. very expensive by the way. All back together and running well, no internal damage to valves, some scoring on the cam bearing journals but minor really. Very lucky this time.
because the pick up pipes have a very fine mesh one them due to the being able to go 20k miles between services.
both time there has been a new pick up pipe fitted and its serviced by himself every 6months. think he was unlucky the 1st time as it was not long after he bought it, but no idea what was the cause the second time