I have to pay another £25 a year, for modification insurance which covers everything. As well as my premium being slightly higher.
The problem with not declaring them is, if you were to crash and take out a £30k car and it was your fault. And your insurance was then void, well.....
Research shows that people who modify their cars are more likely to make a claim, so when declaring mods you pay a higher premium.
Doesn't matter what the mod is, even changing the interior in your car can be a reason to void insurance.
As stupid as it is....
Number 3 is an estimate, not an accurate figure.
As for not declaring modifications, your insurance is void if you have an accident. So that's just very very stupid....