Yep - I thought it would be a good idea to switch off rads in spare bedrooms but yes, it does start creating a damp problem especially if your house is not very well ventilated. Our is a 1990 build so has plenty of insulation but it's not very clever insulation, if all the windows are closed...
Assuming Halo is similar to Hive, and it looks like it, all day long, it'll pay for itself in no time - The concept of 'switching the heating on' will soon be distant memory as you can set detailed schedules as to what temp should be at certain times of day, days of the week, whatever you want...