Help! Oil leaking somewhere

Hi guys I need some diagnostic help. Wifeys car has been using some oil for some time now. Maybe 1 litre every 6 months. So after a little bit of an engine clean. I discovered this [IMG]


I know it's a gasket I just don't know which one. Tapet cover or head gasket? Or both ? Yes it is a small leak at the little yellow sensor as well and on the gasket below too !

Suggestions ?
Thanx


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