I bought 2 x twin packs from Alan Mance Holden ebay store (and 10x oil filters), best price around. My cabin filter has 40,000kms on it now, I may pop it out at the 12 month mark and see what it looks like.
I fitted one recently that was different to the flimsy paper one, was a lot heavier and looked to have carbon in it. Was a genuine filter too. Maybe they've improved them?