golf GTTDI 150 overheating !!!

alright guys, just wondering if someone could help me out with this one ?
iv recently bought a gttdi 150, its a great car but can over heat when i put my foot down, iv had the thermostat and water pump chanced but still seems to wanna overheat, i get a light on the dash and a message saying "check coolant".

anyone have any suggestions on what it could be, or has good history with one of these cars ?
thanks.

my cousin had the same problem........

he gave me this address.........

http://www.honestjohn.co.uk/forum/post/index.htm?t=91261

he said he tried most of these but it ended up being the headgasket!!! and his mate who sold it to him did fess-up!!! said he thought it may of been anything else and the head was the worst case scenario!!!!

sorry to put a downer on ya mate, never know it may be ok just something small.....

Good luck!!

Alright mate cheers, yee hope its not the head, its going in the garage later today soo ill find out soon enough.