The 'sandwitch plate' is a weak spot for leaks, and sometimes the oil-pressure switch. They're both behind the oil filter, beetch of a job with the engine in place. Don't think being in a Nove would help much either
This will depress you - it could also be the oil pump gasket. It makes a leak from that area too.
It's not a nice job to do as not only does the sump have to come off, so does the crank sprocket for the cambelt (yup the big E20 bolt done up to 62,000,000nm). In fact, when trying to solve oil leaks, I'd do it if the sump's coming off.
Incidentally, when I rebuilt my LET, the Vaux bottom end set included all these gaskets, and the oil pump one was metal, the one I took off was paper.
there is a large o-ring that could be the problem.
if you remove the oil filter there is a bolt in the centre of the thread that the filter screws onto, if you unscrew the bolt the oil cooler pipes will drop and you'll see the o ring..