I used a 'cheap as chips' Crosland filter once (for a Mini R50) and found it incredibly hard work. Opted for a Mann one second time round and what a difference! Actually installed easily and quickly, when the Zed is due I'll use a Mann for that, for an extra quid or so, its definitely worth it! As for Oil I usually use Castrol as you can pick up 4l for just over £20 (to LL04 spec). But again so long as it's within spec no issues using any other brand if its got a better offer.