I'm furnishing an old barn which has been converted into a guest house. The 3 downstairs bedrooms each have a clear glass Fire Exit door leading to the outside. Are there any rules regarding the curtains or blinds that can cover this door? Thanks!

The modern guidance clearly does not recommend this, but for the need of privacy you could provided a fire exit sign which is visible when the curtains are closed, they run freely, and a 150mm gap between floor and the bottom of the curtain. You could check it out with the enforcing authority to see if they would accept this, how they would react is anybody's guess.