97 ford fiesta heater ventilation suddenly not working?

Hi on saturday the heating ventilation on my fiesta was working fine and then when i got back into the car to drive home there was no joy from it at all.
Its not blowing any air whatsoever and does not respond to the switch. i have changed the fuses,checked filters and to see if a wire came lose but cant locate the problem. A friend suggested going to a scrapyard and trying to find a new switch for the air conditioning/heater so before i try that seeing as it will be a bit of a pain in the hole to unscrew one from an old fiesta then unscrew my current switch then insert the old one just to find theres something else that needs to be done. So any ideas what else could be wrong?
Thanks