So SWMBO was complaining that the car wasn't getting warm quickly enough (not the engine but the cabin). Of course, her answer was to increase the setting on the climate control as, in common with many people, the concept of a thermostat is somewhat lost on her. Nonetheless, she did have a point and I noticed that it was definitely cool on a long motorway trip.
Finally got to thinking about it today. Pulled out the pollen filter (no need for a workshop manual when you can get youtube) and it wasn't just clogged, it was carrying a pile of leaves. Can't be bothered to question the main dealer who has been doing full services for the past few years, but the man in the spares shop (not Halfords, who don't keep them) said they were often overlooked on dealer services.
Anyway, 11 quid and a few minutes later, viola - one warm car and happy SWMBO.
The moral of the story is, if your motor is feeling unusually chilly this winter, take a butcher's at the pollen filter.
Of course, my Dad would have just chucked it away rather than spending good cash on a new one, but I quite like (the idea of) keeping some of the particulate crap out of the car......