Try asking the Chief Clerk about Schoolchildren's visits, which are not just for boarding school children. However, it may be that they only apply when you are serving overseas but they do apply to children from other relationships and allow the children to travel unaccompanied on BA (a deal the mil have). It allows them 1 visit a year - yeah, I laughed too! - as opposed to the each major school holiday a year for boarding school kids......
Not that the ex-witch (still a witch but the ex) has allowed me to see the kids for the last 3 years apart from 1 1/2 hours in a contact centre but now I'm just going to get bitter. RAF advice on break up of marriage was to move out of the quarter 'cos I had somewhere to go (the mess) however, this was cr@p advice as I left the family home voluntarily and have been fighting for access ever since! What I should have done is kicked her out and told dear old PMS to sort out the screaming witch.