The verdict from the garage is all that's needed is a replacement thermostat housing and coolant. There doesn't appear to be any damage to the head gasket. They have also changed a leaking radiator cap, so the most likely cause for the overheating is the loss of coolant through the radiator cap. They spoke to morgan, who claimed that oil pressure of 1 bar isn't unusual due to the location of the sensor. It was fluctuating between 1 and 2, but did drop below 1, but this was remedied when the engine cooled and I topped up the radiator header tank. I future I need to get used to what levels are normal, especially the water temp, as what I thought was normal, quote possibly wasn't.
