Box bits and bobs

This is a miscellaneous bunch of support work from a branch where I'm trying to sort out a UI for #262. Since I'm struggling a bit to get something I'm happy with, and we still have ongoing discussions about what it should be, it'd be really handy to me to get this stuff merged so I can start to make sense of the remaining mess. There's a fair bit of change here, but it's all stuff which is useful in its own right, regardless of the final direction we take...