Yeah, I've used the POR 15 sealer from Frost on my old Jota, although I think there have been several instances of that goop peeling off becuase of there being more ethanol in fuel.
Don't deal with Frost if I can help it because they load up the postage charges even though Inverness is on the UK mainland. Hell, we've got a tarmac road that goes all the way up here, and an airport too! You'd think we were on the feckin' moon the way some retailers go on...
Anyway. Need to get the old stuff off first in any case- the lose stuff I can shift with plasterboard screws, but I dunno if it's a good idea to coat over the original liner that mechanical removal doesn't get. Ideally I'd just have a bare tank inside, but then I've heard that modern fuels can promote corrosion. It's a PITA, that's for sure.