Hi sounds like you have a possible waterpump problem the vanes on the waterpumps have a tendency to come loose allowing the pump to turn on the spindle without the pump pushing the coolant round the engine normally plays up at idle,best way to check is remove the coolant reservoir cap (careful if engine is warm) rev the engine and watch to see if coolant is pushed out of the small pipe into the reservoir if no or very little coolant comes out chances are the pump is faulty.To check the thermostat check top and bottom hoses to radiator make sure both are hot after a road test,the only problem is that the waterpump if faulty can mimick the signs of a faulty thermostat and air lock,the waterpump iwhen removed can be checked if the vanes can be twisted while holding the front of the pump it is your problem best of luck Andy

Ok thanks Dave and good luck any more problems or info needed you know where i am.

Please dont forget to accept this answer if it helps as it is how i get paid.Many thanks Andy