Ha! Whilst dopey, hopefully not that dopey!
Definitely the oil light and i reckon its the combination of using the cover gasket (not needed) and forgetting the shim (just feckin stupid) leaving the o-ring not compressed enough.
Fresh Mahle filter should be here tomorrow and I’ll be checking the pressure relief valve when I have the cover off.
Every days a school day.
Thanks to all for pointing me in the right direction.