Existing house insurance when doing backfill self-build

[Stu789]

Does anyone have any suggested companies for existing house insurance when doing a backfill self-build please?

 

We are shortly going to start work on a self-build bungalow in the back garden - I'm getting/have quotes for site/self-build insurance (Buildcare/Howdens/Protek) but when looking round to renew the existing house buildings and contents insurance all the providers I've found so far have a limit on the value of the building work that can happen under their policy (ranges from £30-75k) - maybe ok for an extension but not for a detached bungalow!

 

Any suggestions appreciated.