Ask HIAL. They are the company formed to operate these airfields when it was decided that NATS should concentrate on being an ANSP rather than an airfield operating company. Mind you it used to be fun, with the ATCO in charge also being airfield manager.
I did a 4 week stint at Sumburgh in '72 and it taught me a lot about airfield ops as opposed to just ATC ops as the idea was to send you there as an initiative test.
When an ATCO Cadet had validated at their posting in Scottish Division (in my case Glasgow Airport) they were given a travel warrant with instructions to report to their Highlands and Islands airport on a specific date (I had 3 days notice).
You quickly had to learn not just the ATC side of things but how the airport operated because inevitably, at some time the ATCO Manager wouldn't be there and YOU would have to make the decisions eg granting an extension for late opening and ensuring the Fire Service were informed.