Thanks for the excellent advice but I'm probably not going to take that route. Apart from not having a spare queen right now, I've promised the site owner I'd not disturb them for a while, as each time I do, the bees attack passers-by. And while it's fairly rural, there are people within 50 metres.
I think my best option is to see how the new queen temperament is. If no better I could move them, assuming I can find another site. That will give me more options (such as the one you suggest). The drastic option - going back to my original impulse - is to put them down.
I'd really rather not, clearly, but yesterday was majorly stressful and I don't want to put myself through that again.
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