Pete recently did an interview on BBC Radio 4 - You and Yours - which investigated a case history of failed cavity wall insulation.
Insuring a Listed Building is a little more difficult than insuring an Old House, or Period Property. Any difference in insurance cost is based on the fact that a Listed Building may actually cost more to repair than an old house. Any work undertaken will almost certainly have to be done using specific materials, and skilled labour which may cost more than normal.
It is possible that unauthorised works have taken place over the years, and at some stage, you may be called to account for this. The new owner of a Listed Building inherits responsibility for any changes not authorised, and you should ask your insurer about Indemnity Insurance which covers you in case your Conservation Officer requires you to make good unauthorised works. Our Building Survey will help with this - John, Richard and Peter are all expert at picking possible illegal works to Listed Buildings - for example the installation of double glazing or plastic windows.
Bear in mind that insurance may be affected if you are in a Conservation Area - although the house is not listed, you are still bound by similar regulations about what you can, and cannot do to the building, especially where changes to the outside are concerned. For example, you cannot take out old windows and replace with plastic windows, without Consent. You cannot install solar panels on your roof without Conservation Area Consent. Your insurer needs to know whether the house is situated in a Conservation Area.