BUS
Presume you joined and were not pressganged, so you have the option to leave if you don't like the terms.
Perhaps there's a Mrs BUS, and little BUSlets - who is going to pay the the BUSlets school/health whilst you aren't paying tax, and if Mrs BUS is a stay at home mum, who is going to cover her health etc?
If you want to be paid tax free, then you could leave MoD and work in the Middle East, but I can't see Dodgy Military Contracts Ltd paying Mrs BUS a widow's pension if you get slotted.
FYI the French military are on very poor pay compared to the rest of NATO.