£330 for a new starter motor?Check the front discs for warping too. Pretty common.
I agree about the airbox, not an issue. Bought my 13 plate with 15k on it, it's now at 20k and uses next to fuck all oil.
The sm17 starter is shite though. You'll need a spare battery to help kick it over if you plan on a ride when the temp it 5c lower. £330 for a new one.