Well, dispersal is written into the genes of the the UK airbase concept - way back from WWII - long strips of concrete with POL stores, ATC buildings, even hangars etc.
If someone selected some old MOD facilities, with a strip, they would likely have a set of fuel bunkers, probably have some dispersal aprons, would likely have some old buildings associated with the job (Catterick Garrison has a lot of RAF facilities despite being now an army base for instance)
So, some of these bases are already former airbases, they have POL, weapons bunkers, ATC, hangars. They'll need some work and some money but it's not like we're standing up an entirely novel capability here. The spares and stores, I get it and you're right - if you get a bent jet, there may be some shuttling back to base for a fix, but basically we used to be the worlds most unsinkable aircraft carrier for a reason - lots of airfields.
Not practicable for long periods of time as you say, not without some re-arranging going on.
There's also discussion about using smaller regional airports - that might be as simple as bombing the jet up, popping up, landing away and standing a QRA alert from that field perhaps ?
You'd maybe need a small land-away team to polish the windshield and stick a new airfreshener in there but for a day or two, not impossible.
It's an interesting idea, although I do wonder if it's more about signalling than anything else.
