see how the temperature goes after giving the radiator a good flush, make sure your thermo fans coming on too. may aswell check that the thermostat is working properly at the same time could be a bit bunged up. otherwise take it to grant and he'll no doubt diagnose it straight away! have some cables here if you get stuck. good to see its over this way will have to pop down and check it out sometime. are you going to leave it in the gti trim or take it back to stock golf?