Depends on time of year. First thing, our thermostat is rubbish. Complained several times to landlord about it and despite attempts to fix I've now given up. We have to set it to like nearly max 30c to get it to come on. It's not the placement of it location wise as tried different places. Anyway, it does work, just for some reason reads temperature much higher than it really is.
So we do something like this at the mo:
06:45 - 08:15 - HW and CH on
12:00 - 14:00 - HW
17:00 - 19:00 - HW
And then we turn the heating on manually for an hour or two throughout the day as and when we feel we need it. At the moment a lot as family are ill and it's snowing!
My bills are about £40 gas per month, and about £100 elec per month. Elec is insance because we are in debit and they mucked up. Should normally be £75 ish.