From a rather tenuous source there are other guys with Lockheed Hercules type ratings on their licences but all are still in the RAF and none are leaving now anyway. I dont know about the guys flying with them whilst still in the RAF but it appears that one is probably in his final few weeks with the military and if one is a reservist he must have left full time service anyway. Acl probably arent looking for anyone, they must have enough guys from South Africa to man the aircraft they own because they have had this type of aircraft for a long time now. I cant think of anyone else operating this type in the UK unless you count the RAF so if you wanted to bring in a "new" type and start flying it around the powers that be must have a set of criteria including just exactly who is going to be doing the flying. No doubt having a couple of trained guys on type would be enough to get through that hoop. Acl could then import crews from outside the EU and save a huge amount on wages. Problems would only arise if they lose the experience they've managed to grab to someone else.