Ok, Here is an update on the car.
I've taken it to the garage as i just haven't had the time to sort out the issue, if i can call it that, myself.
I popped into the garage earlier today to drop off my other motor and i asked what they had found.
Surprisingly, they told me that they had the motor running for half an hour yesterday and for around the same time this morning.
At no point did it overheat or show any signs of a vehicle with an overheating issue.
They had performed a test on the coolant and there was no trace of combustion gases in the system.
I'm not sure if they have pressure tested the cooling system yet but will find out more tomorrow.
I will, should there be nothing found to be wrong, pop to my nearest motor factors and buy a new thermostat and drop it in as a precaution.
Thoughts?