In case this affects anyone else, we were advised very recently by our insurance broker of over 10 years (the AA), that our postcode was in the Environment Agency flood plain hence they had obtained renewal quotes for building insurance which were in excess of ?1000 pa, nearly twice the price of the previous years insurance.
With contents insurance this took us up to almost ?1400 pa. Needless to say we were a little surprised. We quizzed them thoroughly about this but they were adamant that they were correct even though there we could find no evidence of such on the EA website. They said they would be imposing this on any other se23 customers at renewal stage.
As the renewal date approached (next week) we started searching around other companies and managed today to get a fully inclusive buildings and contents quote for less than ?600 pa , even with all the extras and frills such as legal, items outside the home etc. No other company considered FH to be in a flood plain or having any undue risk factors- which of course it isn't as its far away from the Thames and mostly in an elevated position.

We are taking this up with the AA as its total incompetence from someone and clearly someone stands to make a lot of money out of this ' error'. Has anyone else incurred anything similar?