Pretty sure I've found the problem (until I find another).
Pulled the engine under tray and found it plastered with an oily gunk around the centre.... and this sorry looking resonator box:
I assure you there's an orange seal to the left side of that jubilee clip. Inspecting the top op the resonator box behind the engine, it seems dry and clean, but following the plastic pipe from the box and up behind the radiator fans and it joins to a rubber hose just below the dipstick and there is a small amount of gunk there also.
So I've found one thing to fix but I have a further question:
Is finding oil there normal when the seal fails, or is this highlighting a bigger problem?
If that's a stupid question then I apologise, I'm learning
Regards
Chris