The best place for buying fans or any boiler spare part is MDS who are based in South London. They are Worcester profile stockists which means they have a absolutely fantastic stock of all boiler spares and boiler parts. Just about all spares are held in their ever increasing stock list. Printed circuit boards, fans, pumps and gas valves to name but a few. If you can get to their trade counter you can reckon on good service and great advice.
MDS are the parent company of clickonboilerspares. a great way to get online boiler parts. Worcester boiler spares are stocked in depth so it is rare to be disappointed but even the most obscure parts are supplied within a day or two making boiler down time the absolute minimum. Whatever the fan whatever the part it is probably on a shelf at MDS. After twenty years in business this is a company that has not lost touch with its customers needs.