Hi, the heating and fresh air vents are hopeless on my Fabia (2003 model) the blower fan makes a racket but not very much air is blown through, hot or cold. Could it be a blocked pollen filter? if so how to replace it please. Thanks for help.

:yes: Blocked filter (top-right of passenger footwell) and/or full of leaves:

http://briskoda.net/forums/topic/60114-how-to-fix-noisy-fabia-ventilation-fan/

Check that the filter housing is in right way round. It is L shaped. It will fit backwards and will then blow cold air into the passenger footwell and be noisy; nothing gets to heater or screen. I'd dump the filter anyway this weather.