Poked about under all the various pipes and gubbins in the engine bay (I'm new to diesels and these newer ones are stupidly complicated). I couldn't see any signs of an oil leak from any components using the endoscope, just 'remains' of the leak. My STP engine degreaser arrived, so emptied about 1 & 1/2 tins of the stuff above and below where the oil has been found. Let it sit for a few minutes then gently hosed it off and hosed the pavement down. You could eat your dinner off the engine. I'll keep an eye on it now I know it's all clean.