Had an issue a while ago with one of the recirc motors. Drivers side one which from memory controls the outer door.
Whilst diagnosing I managed to loosen the inner.
After replacing the motor etc it all now seem to operate correctly.
Carried out a recalibration and all seems good.

However, now I often get a humming noise whilst travelling at 50mph and above.

Pressing the outside or recirc has no effect on it.
(Previously when the motor failed and had similar noise, opening a dash vent stopped the noise)

Anywhere else I should look?

Have you got aero wipers? I had them on my previous RR and all they did was hum or buzz at high speeds.

Just a thought. 2015 Range Rover Autobiography 4.4 SDV8

plastic under window, cracked foam under top of fenders

As Jimmie said, the plastic trim around the wipers gets air under it at speed and vibrates against the windscreen...

To rule it out/in put tank tape along the length of it on it and the windscreen and take it for a run... when mine did it it was much worse in cross winds.... There is a foam seal under it that degrades... a new one is several hundred, I put the thinnest bead of tigerseal just under the top edge where in meets the windscreen, it worked well... I'm sure there are other ways to sort it...  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-