Ventilation problem - blocked filter or summat?

[Golfer]

Alrighty...

Problem with my ventilation system  

Had my Mk3 serviced just before xmas, including an aircon service (regas etc etc).  Since then I have noticed that I get far less power from the fans and the aircon takes ages to clear the screen (used to work like magic - 10 secs and away you go).  Aircon works well enough, but there's just no power from the fan system.

Basically I think the filter must be blocked - the garage denies anything to do with it!  (Wheelbase - Hersham - arrrggghh - never again)  

SO, I want to get it sorted - what could it be?  I think some sort of filter - pollen filter? - but where does it live and how can I check?

Any other ideas?

Cheers

Ed

[adyh]

The filter is to the right hand side of the engine bay (looking from the front of the car) , underneath the black plastic in front of the windscreen .