Re: Oi Chavvy boy!
Fair enough though isn't it! If you have non-standard alloys for example, you should be insured for it, it makes the car more likely to be 1) vandalised 2) stolen or 3) have the wheels stolen, hence you should pay more. Where do you draw the line? You don't, hence why all mods should be declared and if your insurance company requires as such, you should pay more.
I paid "****e" loads for my insurance also, however, it didn't mean I change the engine to a Uno turbo, add alloys or a spoiler simply because "i pay a lot".
It's not up to you or I to make such choices, if your insurance policy requires you to inform and pay extra, you have to or find another insurer, not "disagree" with what they are saying and do it anyway!lol
I personally think a subtle spoiler shouldn't make a difference and in some cases won't, have you asked?