So, the shall-I-get-my-hair-cut-off post got lots of positive or ‘can't hurt to try’ sorts of responses, and only one remotely negative one, so I went out at lunchtime and did the deed.
I'm slightly surprised at how much the result still looks like me – I was vaguely expecting not to recognise myself in the mirror at all, probably because I recognise other people by their hairstyles quite a lot. But evidently I know my own face better than that :-)
I think I need to get used to it before I can decide whether I like it like this or not, though. Right now it just seems a bit unreal.