Does your actual policy state that your car is modified?
My insurance with Direct Line ran out last week, and since they don't allow any modifications at all if you're under 25 I decided to swap insurers.
Chased around most of the companies and they were quoting about £1600, since I've only got 1 year no claims (only got my first car a year ago) and I've only had this car 2 months. Phoned Prestige up and they quoted me £1200, only a couple of hundred more than Direct Line, so I went with it.
Now I went to sort the documents out last night and the actual insurance document (from Aviva) says that the car isn't modified, although I told them over the phone that I was going to put new wheels on it as soon as the policy started.
Has this happened to anyone else? Is it something to be worried about,or is normal?