Found the oil leak.....
When I bought it I could see it had been 'down the road' a few times but I wasn't expecting that.
Also, while I'm on: I've had all the plug leads off and didn't mark them. (doh!)
Looking at the points, I assume the leads from one coil serves cylinders 1 & 4, whilst the other serves 2 & 3. But which of the two coils goes to which??