Thank you.it was a while ago now.. it was one of the connectors to the little solenoid valve that controls the turbo.. the valve is near the expansion tank.. which is why the bubbling over coolant sprayed all over it and made it corrode.
I have the valves there on my AMF A2 but my girlfriend's car is a BHC so has them mounted in the vacuum chamber on the inner offside wheel arch. I have bought a used one so will first check the contacts on the existing one and then change it over if the problem persists.