During my weekly dipstick checks, I noticed that the oil level was slowly reducing.I checked underneath and found quite a bit of residue.It looks like a small leak which may have been happening for some time.I degreased as much as I could then pressure washed the bottom of the engine to clean it up for a better look.I think the leak is emanating from the crankshaft seal.The belts are due a re-tension so this job can be done at the same time as I believe the belts need removed to replace the front engine seals.
Update
The leak was indeed caused by the front engine seal.There was also some balance shaft seals on the way out so they were replaced as well.
Parts list:
999.113.281.40 - Oil seal : Balance
928.105.139.02 - Spacer sleeve
999.113.351.40 - Oil seal : Crank
999.707.283.40 - O ring