Oil Smell in cabin/Oil under engine foam cover

[markjm58]

XC90 MK2 D5 - 2017 77k miles,
Evening all, hope you are having a good saturday evening!

I'm not particularly mechanically minded so hope you can help 😆 last few months i've had the faintest 'oily' smell in the cabin upon start but nothing on the driveway, car isnt consuming oil the level on the display seems consistent, and the smell disappears almost immediately.

Tonight when filling up screen wash noticed oil at the left hand side of the engine cover which i removed, pictures below of what's underneath.

What am i likely to be looking at, and how many of my hard earned pounds am i going to have to give away to resolve the situation 🤣

Highlighted in yellow where i saw the oil mark beside the cover, and where it runs along. Its more residue than anything else if that makes sense. Oil level on sensus seems fine and consistent.

[Haldex]

If I had to guess- the valve cover gasket. Shouldn’t be too pricey to fix. If you’re not under warranty - I”d go to a non-volvo affiliated shop and get this sorted as cheaply as possible.