Quiet in here today so a small update on this. I swapped the fuel filler door for a good one from Prestige
Its a very slightly different shade as it's been painted, but its better than the original!
Doing some tinkering under the bonnet I discovered this:
Clearly 'lifetime air filter' translates to 'never look at the air filter again' according to most mechanics
Straight in the bin with that and a stock paper filter fitted instead.