Yep, I've just gone through the whole process again....... going to write a full write up for advice for people, but I found that the cheapest with my wheels added were:
Elephant, Admiral, Bell (all part of same group)
Then Direct Line....
If you ain't got mods then privilege normally cheap, but if you going to mod at all then FORGET IT NOW!
They rip all your limbs off on notification and renewal due to mods.....
Anyway, found the Elephant, admiral, bell very easy to see how much a mod will cost you in change to policy through the web quoting system!
PS: Probably worth saying where you are in country. For example mine is expensive considering I'm getting older, 10 NCB etc due to postcode....