Oil leak

[Gnasher]

Thanks for the suggestions, I had the same idea to use high temperature gasket sealant but wasn't sure it would work,

Put small bead of sealant in the Oring rebate, on the cooler and out the Oring in, then another small bead on the engine casing land, you'll be about to see where the Oring mates with the surface. Push on the cooler, try not to rotate it while doing it up, with a bit of luck it will seal. 

I didn't have much choice either way with oil pissing out of the thing

It happens like that hence me saying "where possible"