Update.
Took the head off. Alloy smeared on the walls of 1 and 4. Still turns over. The alloy from the piston maostly picks off with fingernails but rebore would be required.
Just de-registered it, bit sad really. The decision making process was influenced by fact that we don't really need it, it hasn't done many k's in the last few years. Made two phone calls to local specialists but now thinking it might be more intersting to enthusiasts being in good condition otherwise. Might post something here.