Bit of an update. Car was good for nearly a week, then had the same problems again, this time temp was staying high for longer. So went home and bled the system for longer this time also raised the car up higher, seemed to be a lot of bubbles coming out. While doing this I noticed there was coolant on the radiator fan shroud and traced the leak to the over flow pipe/hose. It was quite loose on the fitting, so I put some duck tape around it to get a better fit (didn't have any sealer). so far has been over a week without any issues.
I am thinking that air was being sucked back into the system from the leaking pipe.Could this be the problem?