Overheating

[Simon Wallwork]

Today the red 'overheating' symbol came on on the DIS.

The temp gauge was at about 120 Degrees C.

Stopped and found the rad to be cold. Coolant system full of coolant and no leaks.

Headertank very hot, boiling in fact.

Car trailered away to the garage- clearly a circulation fault so either pump not pumping (belt???? Pump???) or thermostat stuck closed??

Any ideas?? What drives the w/pump on these? The timing belt?

I've a funny feeling they didn't do the water pump at the last belt swap (70,000). Miles now 130,000.