British law is quite clear. Any person who injects you without your consent is guilty of common assault (it has always been the case - it is just that the vast majority of us either didn't know - like me - or just followed orders). The Forces cannot order you to have a jab.
Furthermore, legally, the only people who can stick needles in you are qualified medical and paramedical personnel. We have med sec people doing it for their war training, provided you consent to it - then that circumvents any legal problems.
The current anthrax jab procedure is a briefing from a medical officer, you are given a video to watch and a 7 day period to consider your options. If you decide not to have the jab, then you can be and are ordered to sign a document that states that you have refused the injection and that you accept the consequences.
I doubt whether you would get away with a subsequent law suit.
Sorry GB2, QRs cannot override the law of the land.