There are some good threads on this if you use the search function.
Gott & Wynne have done some good quotes on the Aero products.
Headley, I was personally unimpressed with, based on my last 2 quotes.
Chubb are supposed to be good but not the most cost effective.
Aviva, same as Chubb.
Last time I renewed, I shopped around and ended up saving circa £400 and ended up with the same cover and agreed value.