Thank you for your reply.
I hadn't thought of plot bands, although I had achieved a similar result using a radarColumn series. I don't suppose there's any way to only colour the parts outside of the blue area series (aside from making the series opaque, which works but hides the grid)?
For the labels, they are mostly ok, except for near the top and bottom. The ones to the left of the chart need to end at the grid point, the ones on the right need to start at it (as they do everywhere except near the top/bottom).. and the top one will need to move up a bit.
Presumably I need to use the visual config option for this, but I'm not really sure how to go about it.