I'm with Hastings, ~£80 fully comp but with no extras, I'm also over 40 with max NCB.
I have declared the Ivans mod on the basis that if I need to claim and they find this type of mod on the bike they may refuse to pay out. They checked with the underwriters who said that given my age and experience they had no problem with the mod, and I've checked that this is on my records with them.
I also declared my Nitron shock in the vague hope that if I need to make a claim they would cover the extra cost of replacing it.
Every other mod I told them about they said if it's like for like (indicators / end can / levers / seat / brake lines / screen ....) then I don't need to declare it.
I've had to make a claim with Hastings previously and it couldn't really have been any smoother, so they get my vote and repeat business.
I did check out Bennett's previously, they have a list of like for like mods that they will allow and anything not on the list you need to declare, once you do the price goes up considerably and when I asked about the Ivans mod a lot of teeth sucking happened to the point where I said don't bother.