OK, here is what I found out.
There are 2 different filters available.
One is normal: 64311496710
Costs £18:25
The other is marketed as
Active carbon filter (which in theory should be a better filter) 64311496711
Costs £19:19
But my local parts department didn’t know the different and said “for the
MCS, it’s the one ending in 710 that they use!”
I might try the 711 to see if that helps.. but £20 quid for a pollen filter! Audi use to charge me some thing like £8.99!