Air Source Heating Running Costs and Heating Problems

We moved into a new build 4 bed detached property (approx 150m2) with an Mitsubishi Electric 8.5KW air source heating system installed with Polypipe underfloor heating with wireless room controllers throughout (no radiators). The system is running 24/7, with the hot water on a timer to heat between 2am until 3am and again if required from 3pm until 4.30pm.

During the buying process we extensive research running costs for air source heating systems and we'er advised that our heating, lighting and hot water costs for 3 years would be £2265 over three years, so £755 per year.

Since moving in early December we have already spent £382.75 on the air source system (this does not include our household appliance usage). We live in Cumbria, December was pretty mild, January has been a mix starting off mild but the last few weeks we had temperatures down to -7/-8°c at night and 0°c during the day, February has been better with recent days seeing highs of 10/12°c.

During the very cold weather the house struggled to achieve 1°c of heat that rooms needed to reach their "comfort" temperature. They are not huge rooms, but many took 12-15 hours to achieve an increase in room temperature of 1°c and some had switched to the "setback" mode for night time before they had achieved the comfort temperatures. The comfort setting is from 6.00am until 11.00pm, when it then switches to "setback" for the night until 6am. Today, the living room still hasn't achieved it set room temperature of 18.5°c, it is currently 18.8°c but as it has achieved the addition .5°c to stop searching. Likewise the master bedroom hasn't achieved its temperature plus .5°c to stop searching.

Our room are generally set at 17.5/19°c comfort for when the rooms are occupied.

On to my first question, does any have the same set up i.e air source pump, only under floor heating. How much does it cost per day to run your system? During the cold weather at the end of January our system was costing £10-12 per day. In the milder weather we are £6-7.00 a day.

Our Polypipe programmable room controllers state in the manual that by the time they switch to comfort setting at 6am, the heating system using the "optimum start" setting should have heated the rooms up to the comfort temperature BY 6am, not start heating FROM........... however despite this function switched on the rooms are never up to the required temperature and will start to search for heat from 6am, throughout the day.

I have this afternoon set the Polypipe room controller in the study to BOOST for 1 hour, but the room temperature with the door closed hasn't changed.

Has anyone had any similar problems with the air source underfloor heating set up? If so, what was issue? Any advice appreciated. Any questions/further information required please let me know.

Thanks in advance for any information.