sorry MrC, but I'm being a bit thick - I think it's the stress...

just re-read your post and I'm not sure if I understood you properly the first time -

Are you saying do the valves etc, forget about dropping the engine and cleaning up the pistons?
But if you do go the piston clean-up route, why not bung in these new better ones?

BTW Apparently the valve guides are 'totally shot', but the cam, rockers are all fine - suggesting, if the odo is accurate, a hell of a lot of idling in traffic, or short journeys?

thanks again