UPDATE: Saw my GP yesterday. It is definitely trigger finger. The fact that it has happened simultaneously in both hands make me quite the rarity, apparently, especially as it's my index fingers. I've had a steroid injection in the base of the left index as it's the worst of the two, if it's going to work it will take effect within a couple of weeks. Right at the moment, it's as sore as f***. This is annoying as I've got a rehearsal tomorrow night and a gig on Friday.
I've bought a couple of said stretchy finger protectors, wearing one at the moment on my poor aching left. Typing is, errm, interesting with it on