Mini R56 overheating / mobile mechanic rec derbyshire/peaks

[Midial]

My 2009 mini R56 engine overheating light has come on - didnt drive on it, had it recovered.

The recovery chap said he didnt think it was the head gasket.

Our local garage think it is, however strangely they don't have the full diagnostic kits, so couldnt rule it out being thermostat or water pump. Couldnt find any leaks.

Advised they topped up the coolant and it very quickly over-pressurised and started to blow water out of the expansion tank.

Gave me the details of another garage as they don't take on HG work, however I'm minded to look for an independent mobile mechanic if I can find a good one.

Any recs would be welcomed?!

I've been reading threads to try and understand more about causes of engine overheating - observations on mine are:

Car starts first time
No misfiring
No excess fumes coming from exhaust
Leaks not found (however when looking around did notice some copper specs of discharge)
Not leaking oil (oil also doesn't have a creamy discharge and was done 2k miles ago)
No rattling in engine.
Quickly getting over-pressurised

Id also appreciate any input on likely cause...

I've read threads where people have done the head gasket and still had the problem.

[CarsOrBikes]

can be more than one issue there with the HG potentially being a consequence, even now to the point of hindering correct diagnosis, might well have started with a leak or a thermostat fault, they're coolant sensitive engine's, if it's backing coolant up quite soon after start it's quite likely the HG is now involved,

[mike9009]

My thermostat housing started leaking at 66k miles on R55.

[Drezza]

Sounds like all the symptoms of mine when the head gasket blew, the exhaust gasses were pressurising the coolant and popping off the top radiator hose. Get an exhaust gas "sniffer" kit off eBay, they're only about a tenner and it'll diagnose the issue.