Not quite sure what you mean by "24 dots representing the hours".
Hopefully this doesn't mean that the on/off times have to be in
whole hours?

Your hope is misplaced. But then, I've always wanted programmers to be much
more granular. I hated scrolling through the minutes. I mean who wants to
turn on at 16:18 instead of 16:17? Obviously, if you want finer granularity
than an hour, you'll be disappointed. At the end of the day, provided you
have reasonable insulation and draught proofing, keeping a place warm for
half an hour longer than you wanted won't cost much. It was heating it up to
temperature in the first place that costed you.

Christian.