Graham: Yes, seaworthiness was the main reason behind my choice, that and the fact that out of similar long keeled boats of similar age, the Halcyon doesn't seem to have any cult following, so prices are more reasonable! That said, when I am eventually ready to buy, I'll probably keep an open mind and consider Twisters, Victoria 26, Nicholson 27, Vancouver 27/28...
Of course, I'm still waiting for lockdown to lift so I can actually get some experience sailing! Fingers crossed I don't find the rolling too uncomfortable and end up running to the shelter of a plastic fantastic :P
Arne: Thank you for your advice. I finally have my copy of PJR now, so I'm going to do another sketch with the slingpoint and halyard angle adjustments, and I'll post it up here when I'm done. I'm still doing a lot of looking up terms in the glossary/on google as I try to understand, but fingers crossed I'm getting there!