That's pretty cheap. We keep our old but relatively well insulated and retrofit double glazed house at 20-22 degrees from 5pm until 9pm, then 18 degrees until 7am.
Do you find it cheaper to keep "heating" during the night rather than letting the house cool off and do a short 1-2 hour warm up in the morning?
i.e. I run 22c from 4:30 (sun still out so a bit more heat to extract easily) to around 9pm.
Then turn it off at night. Then have it run from 5:30 am-7:30am during the week at 20c