Why can't they get it at Hurn?
Simple. We got it [in it's previous incarnation] some 12 YEARS ago! Then it only had two US airports and a rather boxy-looking "generic" one, but it did integrate with MS Flight Simulator so you could control on one game for a pilot flying in the other.
Was it any good?
Not really. All the phraseology was very "American" [sorry Yanks] and thus no use for training UK Controllers. This version looks prettier [DirectX graphics] but is still based on the same non-UK phraseology. It's no use to Hurn, but may be of interest for ATCOs to let their kids play with. IMHO though, if you want to watch aeroplanes coming and going on your PC, buy Flight Sim X and install the Heathrow scenery.
We saw this advertised and after a wry smile or two, said "No Thanks".