As Lex-aholic says, much depends on where you live.
At my last renewal, for IS200LE, 53 reg, with protected NCD, best quote I got was the renewal quote from the insurer I was already with, Liverpool Victoria / Frizzell, at £495 incl tax. I live in London.
I tried Norwich Union, who quoted some ridiculous figure, something like £1,000.
A few months later when my household buildings/contents cover was due for renewal, I rang Norwich Union for a quote but was declined entirely. The telephone operator was honest / sympathetic, telling me that he too had the same problem with his own employer - he lives in Glasgow, and Norwich Union do not want business from people living in cities like London or Glasgow and will deter such business by either quoting unrealistic rates or by rejecting it entirely.
The latter unfortunately causes problems in approaching other insurers for quotations, as most insurers require you to tell them whether you have ever been refused cover, and non-disclosure of that is a serious risk as your rejection will have been recorded on the database shared between all insurers.