If you ever need to make a claim to your insurance company and you have not informed them of any changes to the car then they can refuse to pay anything.
It should be worded in the small print in your insurance booklet,if it's not mentioned, or you simply cannot find it, give them a ring and ask them.
Better to be safe than sorry.
This is a sentence taken from my insurance policy booklet.
You must tell us about any alteration you intend to make to your car/s.
Both Primary policy holders and Vehicle Policyholders are responsiblefor this. Failure to notify us of a modification may result in your Policy being cancelled from the start date, additional premium being applied or your claim being rejected or not paid in full.