So, an update. Bann's seen the vet (and decided cooperation is for other guinea pigs, and not for him lol) - we're in agreement the eye looks much better. Still 99% sure nothing's caught in there but not 100% because, ahem, cooperation issues. We're also in agreement it's not 100%. I've got another tube of the isathal, and I can change the doses down to once per day. If I'm happy within two weeks that it's sorted I don't need to continue with the drops but if I'm not happy with it within two weeks I'm to take him back to see if there's anything else going on.
And I got more syringes
Other than that he bumped his head off the carrier trying to put him in at one point and I managed to tip a vimto ice lolly out of the wrapper onto my jeans and now they're stained with vimto and I got brain freeze for my trouble.