924 oil leak

Hi folks, before I take the long and potentially expensive route of lifting the engine out :headshake :headshake
I have a slight but irritating oil leak from the rear of the block. It's not the oil pressure sensor and I have checked and rechecked the valve/rocker cover gasket.
Is there another potential cause for an oil leak at that end of the engine? It is not running along from anywhere ahead of the rear block face, have cleaned the engine so often you could eat your lunch off it, so I am a bit stumped just now.

Rear main crank oil seal! drop the box, remove the clutch/flyweel, pop the seal out, slam in another, sorted!

Yep, only place left I guess. So it's getting a new clutch this winter too! Cheers.