Thanks Peter.
Neither of my local Indies want to touch it.
The second one I visited this morning said the most likely thing was cam sprockets wearing (£400 each). He said either run it until it's time for the breakers yard, or trade it for something else.
I think I'll just keep going for now.
Have heard about the breather pipes too - buried under inlet / kompressor, pig to get at...
Mine has 101k on the clock.
My usual chappie for the larger jobs is not available for a few weeks after an operation...