Hi Charles,
With regard to the air vents, they operate via a small plastic clutch assembly which is a well known weak spot. You can buy the originals readilky enough at a Jaguar dealership but, better still, there is an enthusiast who manufactures an aftermarket item which fits peerfectly and is showing very good reliability.
Go to https://www.cs2000-z-tech.co.uk/ and navigate to XF modifications.
Fitting them is relatively straightforward and there are several illustrative videos on FB.
Personally, I have several spares in my bits box as they are cheap enough.