Overheating on STI
 

I drive a blobeye STI and its suddenly started overheating once driven for more than 10 minutes. (No smoke or anything, just the temp gauge) While sitting in traffic the temp gauge goes all the way to the max. Once I pull off it drops very quickly, back to mid temp. At the same time whilst the temp soars to max, the heat being blown from the engine turns cold. When I move and the temp drops back to normal, I get a sudden rush of heat. Any ideas please?

Not being funny but have you checked your coolant levels ???

Check the water pump and waterpump drivebelt