I got the impression that "SA80" (standing for Small Arms for the 1980s) was a designation that covered the family of weapons, including the L85A1/A2 rifles, the L86 support weapon and a carbine version of the L85 that never went into full production (and I think some sort of cadet rifle).
Anyway, back on topic: I use nearly all the medic weapons, it really depends on the map and the combat situation. They're all different, and have different benefits.
For really close and personal combat, like Karkand or Warlord, then the AK-101/AK-47 with full-auto fire and high damage are the business. That's where those guns shine, for me.
I use the L85A1 for specific jobs. It's okay in close-quarters because of its auto-fire, but it's best at long range in single-shot. I love it on maps like Wake or Surge, with big open spaces. It's basically like a miniature version of an SVD, and it's got just enough damage to kill with single headshots.
The G36E is the most versatile. Not as good in very close quarters as the AK's, because it's only burst fire and not automatic, and not as good for sniping with as the L85, since it doesn't have the scope or the headshotting ability, but at medium ranges the burst fire is excellent. Generalyl, unless I have reason to use one of the above rifles, I'll take the G36E, at least until I figure out what style of combat is prevalent on the map.
The only one I don't really use is the M16, mainly because I don't see what advantage it has over the G36. Probably time I gave it another chance, anyway. Medic is almost at the bottom of my "most played" list at the moment, I guess it's time to go back and perform some shock-paddle-related miracles for a while...