Well, I registered the Nook last night, using a spam-catcher email address and charged it up to 97% before I hit the sack. This morning the charge had only dropped to 96%, so it's looking good so far. Fingers crossed it won't have dropped any further since then [I'm at work at the mo', so can't check again til I get home].
Thanks to
john306 for the original suggestion that not registering with B&N is responsible for the massive battery drain
