Sorry if this is a dumb question, but do the insurance company really care about whether you rebuild or not?
I'd have thought their responsibility is to pay you for the agreed reinstatement value, and then it's up to you what you do with it. You can use it to rebuild, or to buy a new house, or blow it on the Grand National.
I've no direct experience, so I'm just speaking in theory, based on experiences with other types of insurance, but is that not how it works? I can't see why an insurance company would get involved in a planning issue.