Well... yesterday I went to start the car up after a bit of frost on the windscreen, so went to put the interior fans on and nada, nothing. Hurriedly start looking up HVAC issues on here and tried all the usual quick fixes - HVAC reset, clean contacts on the connector under the glovebox, battery reset, still nothing.
So this morning I went to the fuse panel (should have gone here first) and had a nose around. And what do I find.. a burnt out 25amp fuse where a 30amp should be in position 5 for air conditioning and ventilation unit.
Quick change out for a fresh 30 amp, and all working again, back to automotive bliss. At least I now know what is required if/when the heater blower motor conks out (dashboard out job £££).
I am going to be charitable and say maybe it was the only spare around. I proceeded to cross reference the rest of the fuses and found position 21 - direction light intermittence should have a 20 amp but had a 15 amp in it.
At least they were underrated and not overrated fuses. Oh well there ends a rather boring tale of a couple of fuses, but it did have me panicked for a while.