An inconclusive update to mine, I took the car to two garages today, one of them put a coolant system compressor on the rad, pumped it up to 20 psi and left it ten mins, it dropped a little bit but he said it seems fine :/ He also put the pressure thing on and had me run the car, it didn't built up any pressure then which he said was good....he seems to think nothing's wrong weirdly I then took it to another garage who had a quick look and said as the bottom pipe is cold(which it always is after driving it, only warms up if I leave the car to run) he said that meant there deffo appeared to be some issue but he wasn't sure what, possibly blocked rad, faulty water pump or hg, or thermo yet it is a new one. He said to go back on Wednesday he will have a proper look.