Who in real life deals with this, knows their stuff and can help pinpoint the problem without an agenda to sell you something?
I know I'm going to need to buy something/do something/change something but I want to get it right and solve the issue at cause rather than deal with the consequences as it were.
So are there people whose job it is to do that? Any googling just leads me to people selling expensive whole house mechanical extraction and heat exchange units. Which to be fair is probably not that far off the mark with this house!