Hi sorry for delay. Oil cooler out and cleaned-covered in light brown sludge! Checked for leaks but no signs. Removed rad which was very flaky and seemed to sag in the middle but no signs of blockage. Ended up removing head (big job but not impossible). Got head skimmed and pressure tested (wards in rugby). Rebuilt with original oil cooler, new rad, replaced plastic dowels!, new coolant reservoir as mine was filthy brown from problem and could not clean. New oil and coolant and so far no problems. Oil staying clean and coolant level stable an bright pink. Conclude from this that either a hose was leaking, rad was shot, or cylinder head was shot - dreaded plastic dowels on the TD5 perhaps. Sorry to be so inconclusive. Also removed the EGR valve now runs all the better for this. I had to make an injector slide hammer plus a fly wheel locking tool. Overall took me probably about two days and few long eves to complete, but happy that Landy is back on the road. Thanks for support and hope this info is useful to someone else.