buildings insurance annex listed buildings

firbyfred

Hope this is the correct category. We renovated some out buildings 12 years ago into a 3 bedroom cottage on the in-laws listed property/land, some of our money is invested in it, there is about 30 metres of garden between them, everything is separate electric, council tax etc. when it comes to building insurance during the last 3 years they keep insisting that because it is a listed building it should be insured together making it a 7 bedroom property.
The in-laws do own it all, but I don't see why the 2 buildings can't have separate buildings insurance