There are tons of factors that go into insurance, hell even credit rating can effect your price (yes companies do soft searches against you).
Postcode, albeit Manchester is probably the most impact isnt just the only thing.
Insurers constantly change their pricing strategy and risk appetite in areas. If they covering too much risk in an area, an insurer that may have been good for you 2 months ago because others were quoted cheaply could now be extortionate because of a review of their books.
Its so individual that its almost pointless asking what others have been quoted, simply price compare with all the sites available then look at the direct only ones and google for the more obscure/smaller insurers.