Hang on Stu, you are right (partly), I don't think they dock pay. The Army will make sure that they pay the bill though. I had a high ranking officer that forgot to settle up before he left. Gave name and address to unit and they got intouch with him, job done.
As for docking pay, don't think so, only when it's about paying maintainance maybe. Get intouch with their unit and they will put you into the right department, job done, honest.
I usually try and get the estate manager as a custy, that shortens the process.