Top tip Jinjur - thanks!
Worked a treat.
1. Mircofilter removed - 6 x 8mm hex bolts (how dealers dare charge more than £30 to do this (inc parts) beggars belief).
2. Zoom in on right hand vent
3. Further zoom (red box shows next picture)
4. Here you can make out the fan behind the vent - complete with rusty bolt in the centre. Quick squirt of WD40 through its straw straight onto the fan. I had the fan on high speed with all the windows open.
Smelled a bit, but WD40 doesn't smell too bad. After 1hr or so driving, hardly smells at all now.
Most importantly = NO SQUEEKING! Result.