Thank you - looking at the link, it seems it might be that. I wondered if it might be a fuse, as in the handbook there are 2 fuses, one for full fan power and one for the rest, so will check that first. Would a clogged cabin filter just reduce the air-flow rather than what we have, which is no air-flow at all?
If the fuse is ok, might see if I can locate the heater resistor and see if it looks like it's no good, sounds like a fiddly job though!
B-Max Zetec Ecoboost
Deep Impact Blue
No-frills other than rear parking sensors...