The mayo/oil I could see I hope is from previous contamination as when I took the sump plug out after draining much, it was quite a disgusting site. The head was skimmed/copper gasket fitted but the filter I'm guessing was totally full of this same sludge that looked like it was from the rear end of an ill guy after a boozing/curry session lol.
I had replaced the cork gasket for a rubber one but noticed when buying there was a notched one and unnotched variant. May need torquing up a little more but will investigate.
The oil/mayo I noticed was on the bottom of the exhaust.
I really hope the block isn't done for

.
After running the car for quite a while, probably an hour or so the dipstick looked like it had cleaned up.
Oil level also didn't seem to rise but it wouldn't while it was also coming out of the cam cover I guess!
And I had previously sorted leaks out at the intake manifold where rubber has perished and also at the coolant sensor. Breather was pretty clean as was the exhaust after running to.
Took her for a very short run down the drive

and had a big smile on my face from the twin cylinder noise in the back.