Help Help :-((

Hi all I have an E36 323i saloon radiator was leaking so I fitted a new one whilst I had it apart I fitted new water pump and new thermostat. Once all back together I am having a nightmare bleeding the water system. The temp goes up to half way and stays there heaters are blowing cold I have had all hoses off and seem to be getting water to all parts of engine etc. It runs fine temp doesn't go up or down but when I remove radiator cap it throws water up in the air and just keeps pressurising, I took thermostat back out and checked it in a pan of boiling water and its opening fine so im thinking head gasket now although after speaking to a few people apparently they can be a bugger to bleed any help would be appreciated cheers Andy.