Well, we know that Dane is on loan to Euroforce--but didn't Dane say something about it only being a temporary assignment? I'll have to go back and check.
It doesn't really surprise me to see any of the members on their own--MI13 is a bit more loose-knit than formal teams like the Avengers. Basically all British superheroes are part of the organization, and they'll pull together whichever ones they want or need for particular cases. And we know several of their members have their own outside concerns as well--Captain Britain and Meggan run the Braddock Academy for young british superhumans (with some other MI13 faces as instructors as well); Blade is currently with the Avengers, etc.
Yeah, I think the last time the Dane/Sersi relationship came up was back in the CB&MI13 series, where it was implied she was the one who turned his heart to stone.