Space A is theoreticly possible for members of UK armed forces. I have known people who have done it. What they really need to see are your 'leave orders', so have a copy of your leave pass as well as a NATO travel order. there is a priority system, as non US serving you will be lowest. This was the case about ten years ago and I gather it hasn't changed much. Can anyone verify it's still the case?
As a tanker captain I was ofeten asked when flying round the US if we had space A. I usually asked the question, but it was usually TFD. Only once could we do it.
As for indulging. Don't start me on that! Yes it's allowed - but it's controlled by the movers. So that's largely the end of it! I did a trip to Cyprus in a tanker once. Two seats were made available on the op order for indulgees for the GE and one of the groundcrew to bring their wives for a weekend in Cyprus. Just prior to departure, the GEs wife phoned to say there wasn't space after all. So we were surpirsed when a van arrived with the indulgance pax which turned out to be a mover and his wife who saw two seats on the way to Cyprus available and decided to snaffle them. Just before Cyprus, time for the tanker/tanker bracket - the other tanker couldn't trail his centre hose so we had to flip/flop and we continued to Bahrain. I left it to the GE to explain to the indulgees that we were now on the way to Bahrain where there was a curfew and that they had to stay in the Diplomat hotel at their own expense. I think he enjoyed it!
When I left the mob, I joined the RAFA as a lifetime member and got an RAF Retired ID card. The US forces recognise it just as the same as their veterans cards and I have used it for access to BXs, purchse discounted theme park tickets and get hotels and hire cars at special rates.