I had a proper look through the beehives this afternoon; they've all got from one to two and a half frames of brood, with varying sized patches on each frame. The colony I got in December is far and away the biggest (it would be with such a massive cluster). It still has the odd bee with shrivelled wings, indicating virus, but the number isn't increasing. I managed to get to the local Association AGM last night for a change, and got stuck on the committee. Apparently it's only a couple of meetings a year so it won't be onerous.
I've done a bit of digging as well; it's going much more easily now that patch of ground elder is dealt with.