Although the medals of most of the naval characters were correct, those of CPO Evans were the wrong way around. The South Atlantic Medal (for the Falklands War) outranks the Royal Naval Long Service and Good Conduct Medal; and that's a matter of statute, not preference.
MEM O'Brian (played by Andy Serkis) arrives at the court martial with only three good conduct badges on is left arm. Although referred too as "MEM" O'Brian throughout the trial several scenes during his testimony, an Anchor "LMEM" appears and disappears half way through that scene.