marks, if you search you will see other posts about this periodically.
The only responsible advice is to consult your insurer prior to doing any mods, then declare them and pay the premiums. Better that than have the insurer find them on the car when you claim. The T's and C's of car insurance policies are clear and when it suits them, insurance companies do exercise their rights to void them.
It does look good value to add mods if you compare the premium for each with faster (usually more expensive cars) that your mods allow you to match

Thats how I explain it to Mrs T anyway
