I'm sure the RAF could spare 20 minutes or so for someone else to have a go too as it is after all outside a restricted/danger area so they don't own or control it.
I've seen some photos on another website, taken by the spotters who sit on the hill taking overhead photos of the fast jets. I've considered flying the circuit myself - I'm told you don't have to go that low and you call ahead to see if the circuit's clear. Problem is my radio hasn't got the range.
I wouldn't fly the loop without calling first. Neither would I assume the RAF would be willing to spare 20 minutes at my convenience. It costs about £60k per hour to keep an Eurofighter in the air so if you make 3 of them fly in circles for 20 minutes waiting for you to clear the training area, then it's an expensive trip for the taxpayer. They use the Mach loop often, but not so often that it's hard to find a time when it's empty.
Flying in Wales is wonderful. In contrast to the airspace around London where you have to be continually on guard to avoid shutting down Heathrow or Gatwick, you can pretty much do as you like. I would hate to see the military gaining a huge swathe of airspace when we can easily avoid conflict just by talking to each other.