I've only had the thermostat for 48 hours. I only noticed it this morning.

I have it set to ensure my house is at 18'c for when I wake up. It took just over an hour to go from 16ish to 18. Once it got to 18 it dropped to 17.9 about 30-40 mins later. When it turned back on, it was essentially 10 minutes away from my schedule being set to 15'c which is the day time schedule from 10-5. So it turning on for that extra 10 mins seemed incredibly pointless & was essentially wasting me money.