Thanks for the responses. The engine has done about 74k and was a full Vege recon unit in '04. The plastic thermostat housing (with bleed screw) Part 1336-A1 sheared and disintegrated inside the rubber top rad hose!.
A sort of no warning jobbie on a very hot day. The water use (level drop) is light and she'll run OK for a bit longer, just with the occassional large hiccup!. Bottom end and rings should be fine, though one Pug forum suggests rotating the liners 180 deg to change the thrust face. Others say these motors go 200k-250k... which I can well believe. Still getting over 40 mpg mind you.
I know the liner O rings have a temperature limit not far above that of the red warning light ie about 8 - 10 deg C. Also if the liners shift when the head is off, it is unwise to reuse them. Never quite sure what will stick to which surface when you lift the head....using a broad wood chisel to separate a gasket is not unheard of...

Might get a set of the O rings anyway as the 'rubber' will be fresh and un cooked!. At least they'll be there if needed and only about £6 a set.
I will do the stem seals, as I know they are a bit less than perfect, again mostly a bit hard and old, and some light oil can be seen on start up, even well before the gasket playing up. Hopefully the drill press or my G clamps and a bit of jiggery pokery will sort the valve/collet assembly fairly quickly.
Planning to keep all the other parts ie manifolds on head as they are OK. May have to do a new exhaust to down pipe but a minor problem in the scheme of things. I don't know if the head has been skimmed or not as a refurb, I was planning to check with a straight edge ( I have a 600mm one) and fractionally reface with a flat block and wet and dry and a diamond stone if a little out. If bad, I'll get it skimmed.
Just getting all the bits together in advance so hopefully I can get it all done in one hit rather than be stranded waiting for some part.....
Thanks, once again.