Brilliant, thank you.
Fortunately I don't need to now, but this rope trick is very useful to know.

 

I think I've found the coolant problem.
The seal at the base of the thermostat housing was bodged with some gasket sealant and looks like it didn't seat properly.
Still pleased to have heads off as the surfaces were scraped badly by whoever changed head gaskets and the timing slippers were cracked!

 

What a great idea CABEL. You get to my age and think you have heard it all but that's a new one on me.