Then our Asda shopping was delivered, only the driver managed to get stuck on our track. After a bit of musical cars we got the Disco out and pulled him from the mud. Not made easier by the lack of a towing eye on the front - it was one of those removable screw in ones which was nowhere to be found.

Then took a look at the caliper. It was difficult to tell for certain, but the oilyness didn't look fresh. It was actually the passenger side hence why I hadn't seen it when doing the cambelt. It looked more like the CV boot had split previously, and coated the caliper in grease (boot looks fairly new on that side). Anyway, I've cleaned it off so will get an assistant to press on the brake pedal and see if anything leaks out. I have a seal kit for the caliper so should be able to repair it if it really is leaking.