The fan is staying on all the time (even when engine has long since been turned off) so we think that the sensor is defective.
We have traced the problem to the sensor switch that is on the rear of the radiator (on the inboard side). However, the issue is that we can't see the relevant component on the Exploded Parts Diagram anywhere -unless anyone else can spot it?:
http://www.oemepc.com/audi/part_sing.../lang/e#sec_45
If you look at the un-numbered entries between Component #28 and #29 on the list there is a possible item listed - Audi Part # 034919369B
However, this doesn't quite look right (different elec socket on it)
https://www.onlinecarparts.co.uk/oen...34919369b.html
Any advice/assistance would be appreciated!