So, yesterday I drained the coolant, cleaned the tank of the black oil. (it was black).
Today, clean tank refitted, Forte bio degreaser and cleanser (pre-mixed in 6 litres of clean water) thrown into the system, burped it and ran it at fast idle for the stated 30 minutes.
Drain that out, refilled with fresh water and ran for a further 10 minutes, drained that out.
Fresh new anti-freeze put in and ran to temp, cooling fan cut's in nicely, temp gauge sitting perfect on the half way point.
Really it needs to be left overnight to see if oil appears, but I returned car and instructed her to check for oil over 2 or 3 successive mornings and report back to me.
If the oil does NOT reappear then I haven't influenced that result by doing what I've done.
If the oil DOES reappear, then on her instruction I shall use that expensive 'liquid head gasket repair snake oil' and take it from there.
So, in summary....
Degreased coolant system.
Rinsed.
50/50 antifreeze put in.
Thermostat opens nicely.
Fan cuts in nice at correct temp.
NO steam from exhaust.
Simple stuff really (suits me just Dandy, can't be doing with thinkin'...)
Now, theoretically, fast forward 3 days, I get the call, Hello you handsome SOB, there is NO oil in my coolant, what would you do?
Remember, owner checks things regular, it was a Garage that said HG!!
Ooooo, I do hope the oil doesn't return, I H8 dodgy garages!