So, update for those interested - I ended up going with the QHY22 (
http://qhyccd.com/en/left/page2/qhy21-22/). For a few hundred $$ extra I got a two= rather than single-stage Peltier cooler (so down to -45C below ambient, rather than -25 for the Atik), anti-dew heater, a hard pelican case and a 240-12V adapter. I'm sure I would have been happy with either, but I think I made the right choice for me.
Now waiting for it to arrive, followed by the obligatory few weeks of cloud to follow! I also have an 8" f/4 newt astrograph about to order (FL = 800 mm) which will complement nicely my ED80T (FL = 384 mm at f/4.8) and my C8 (FL = 1280 mm at f/6.3).