You can get good results by simple trial and error, but it does take a fair commitment to taking the bike apart and putting it together again. After several attempts I've achieved a passable setup, but it'd still benefit from a visit to a dyno. I could be wrong but I think the Isle of Wight is geographically quite close to Crescent Suzuki, if you ignore the sea?
I've said this before, but any breathing mod that doesn't require rejetting isn't much of a breathing mod- the entire point of the K&N is to pass more air, after all.