Ibiza 1.9 tdi pd 100 hp bleeding cooling system

Hi folks
I've changed the timing belt & water pump today on a Seat Ibiza 2007 5dr AXR 100 1.9 TDI PD 100HP engine (routine service). Everything went fine apart from the cooling fan not cutting in after 30 mins of running engine at revs idle and on the road. Cooling fan works with AC turned on. Temp 90 C when running on road and idle, never going above 90 C. Heater blowing hot as normal.
Are there any unusual bleeding techniques used on this engine, I replaced same amount of coolant ( 5 liters g12+ ) coolant seems to be hot in all pipes and radiator also circulating back to expansión bottle through the small pipe attached to the top of the expansion bottle.
Any ideas or hints greatly appreciated.
Jon

Ok fan working after a frugle drive home from work and parked up with bonnet closed and reved for 10 mins, then she blew (the fan that is).