mine wasnt too bad. all they really increase the premium for is anything that increases power. it seems you can have all the suspension and chassis mods you want and they dont care????
to find out for sure you will just have to ring your insurance company and tell them what you plan on doing so they can qoute you. alot of mainstream companies dont allow many mods on the policy though, so be careful of that.
Im about your age with a few mods, exhaust, piggy back ecu, wheels etc and it put it up by about a 100 mate. I thought this was fair enough. Hope this helps.
if i didnt declare my mods through moneysupermarket i could pay 450 fc, but because i do declare,with adrian flux i pay 900 fc. better safe than sorry i think.