I was with NFU until I fitted a disco rear axle. I thought the disk brakes would only add to the safety, but they bumped the price up to a stupid level, saying they didn't want to deal with modified vehicles.
I have just renewed with Annetts & Orchard, £172 for me and Mrs FL, fully comp, all mods declared and no mileage limits. Can't fault em, and the boss understands Landys, he's on here somewhere.