Yeah you always need to tell your insurer about anything which is non standard, even tinted windows.
If you tried to make a claim and something wasn't declared they would void your insurance and you would have to cover all costs yourselfs. Including your damage, tp damage and personal injury claims.
With us with some of our underwriters it makes barely any difference if any at all (depending on what you've done)
Best bet is to always enquire first before you do it and if your not happy have a shop around and see what you can find.
Hope this helps

Danny
HIC