SKOS,
all U.K. civilian ATCOs are licenced by the Safety Regulation Group of the Civil Aviation Authority.
The standards they set are minima, so the ATC staff at, say, Bournemouth or Blackpool should be as good as those at Gatwick or Glasgow.
Any ATC visit, (including those made to military ATC units), is time well spent if you are serious on a career in Air Traffic Control.