Home House Re-Build Value

When i first moved into my self build house in 2008 the re-build cost was valued at 400k by the bank. (House is 3000sq ft in countryside) I have been insuring my home to this value ever since & the premium keeps rising at a steady rate since.
In the current climate i do not believe it would cost 300k to re-build never mind 400k but do i need to get the re-build cost re-valued by the bank or can i go ahead with home insurance based on 300k re-build value?
Obviously my home insurance premium will decrease significantly if the rebuild cost drops by 100k.
There is 230k outstanding on mortgage.
Any help or sugestions greatly appreciated.

Have a read through:

or input figures into:
[broken link removed]

Should give you a good idea...

Thanks for that link, its very handy.

Have a look on wwwselfbuildrates.ie you can calculate the Rebuild Value for a stand alone type house there, as far as I am aware the SCSI calculator is for Estate type houses only?
Also remember the Rebuild value takes into account the following:

1. Demolishing structure including grubbing up floors and foundations etc.