Thanks. I cleaned it all out so will keep an eye on it however...
A new development from last night...
Was driving home reasonably enthusiastically but nothing particularly heavy. Came down to a junction and the low oil pressure light started flashing around idle which went out again as soon as I put a little throttle down. Came off of the roundabout and switched off immediately. Low oil pressure also backed up by the VDO registering low.
Let it cool down, checked the levels and still half way up the dipstick (was at just below max around 50 miles back). Started it back up, no light and all was well. Nursed it the half mile home.
Started it up today and no light, compression still great, however it's now knocking above 2000 rpm. Sounds like it's coming from the head but I could be wrong.
Put bluntly it's f*cked

. Can any light be shed from this? I could try and record the knocking.