If its from the bottom edge then it does indeed sound like the gasket...
This thread might explain the oil hole better
Thanks. A useful link. I'll look for the hole. I've removed the starter. It's dry in there. Rocker cover gasket also seems dry and not leaking down from there. Should that mysterious hole have a dangly pin in it as the earlier post or should it just be a hole? Is it intended to act as an overflow pipe to warn of oily issues unseen within?