Hi there,
I've been advised my mini has a chemical cleanout but do you know whether to use this stuff if the engine is seriously overheating already?
The head gasket and thermostat have already been changed but it's still overheating, probably due to the fact it's spent most of it's 10yr old life sitting in a garage not being driven!
They were talking about oil above.
You're issue is more likely cooling, I'd check and flush the coolant system.
You could remove the radiator and flush water through it using a hose, and also flush through the coolant system in the same way. Then refit, and fill with fresh coolant mix, (50/50 antifreeze/water mix.
Dave