Overheating Issue

[junglie]

I have a TVR S2 runnig a Ford 2.9i V6 and I am having an overheating issue (also posted on the TVR site). The car runs well and, out on the open road with a decent airflow, it remains solid at 90 dec C. When it is stationary the temp rises to 100 deg C and I obviously shut down - I do not have to sit in traffic so this is only when I am idling on the driveway. There coolant is boiling and steam is coming out of the reservoir overflow pipe. Nothing too dramatic though. I can't hear the radiator fan cutting in and I am not losing any water. Could this just be the radiator fan or possibly the water pump has packed in?