So the sump is drained, the sump bolts are off but the pan is still sitting there smiling. I've run a sharp edge around the groove between the bottom of the block and the sump pan, and have left it for a while... will check again on the weekend. I've put a bottle jack and a piece of wood there in case it comes down suddenly while I'm not looking. Folks tell me that it might have a cork gasket!
While underneath, I'm impressed with the amount of effort gone to earth every part. There are earth braids going everywhere, including to the sump pan.
I guess this is for radio silence, which is good as I intend to get a a suitable HF set for it some time ( de VK2DLY ).
There is a bracket welded to the exhaust extractor which goes under one of the sump bolts. Presumably that was to stop the extractor vibrating off, but it's a nuisance.

