We did some more sparring, tonight, and I emerged relatively unscathed, apart from cramp in my hams, that is. Leastways, I've come to the conclusion that it's only cramp - I did think that I'd pulled something, because it was so uncomfortable, but it eased off after a long, hot soak.
I felt a bit outclassed, to be honest - I was the only ungraded adult - and although I know a bunch of techniques, now, I'm not seeing the opportunities to attack/counterattack. Mind you, even if I could see them, my fitness is such that I don't have the explosive energy to exploit them, just now!
Onwards and upwards... I'm going to work on stretching my hams. I've never been able to do the splits, either, so I think I might aim for that.