Taking those modelled phase shifts if 7.2, 10.3 and 12.5 hours only really apply on the 2 days a year when each hours of daylight, or hours of darkness, coincide with the phase shift.
The other times the building is cooling or heating.
Did you just model a wall?
The two biggest influences are the glazing area/orientation and the uncontrolled ventilation rates.
A thermally inefficient floor can have an impact as well.
The footprint area to perimetry ratio makes a difference to.
Basically once out of the tropics, daylight hours plays a larger and larger harder game the greater the latitude.
The UK also has a strange climate, not easy to model reliably as we can have warm nights in the autumn and winter (last week was over 13°C), but quite cold in the spring. Much of this is to do with the sea surface temperature around the UK. It is this relatively high winter SST that makes the UK cloudy.