of HVAC pdf in repair manual shows an illustration to determine what faults the A/C system may have.
How to read A/C DTC error codes:
To run the self-diagnostic function, do the following:
1. Turn the ignition switch ON.
2. Press the AUTO button and then the OFF button.
Continue to hold both buttons down.
If there are errors a bar will FLASH in the digital display pattern at left alternatively within the number '88' on the A/C screen on the dash")
To limit windows fogging somewhat: I try not to 're-circulate' the cabin air in misty conditions, [drawing instead fresh dryer air hopefully], and open a side window just a crack while underway.
As an afterthought: & Not sure if that 'goggle demisting stuff' used in some winter sports my be a good thing or not for your windows there, but maybe worth a try as the UK can be so humid.
fwiw: I set the heater knob a few degrees above the lowest setting only, to help the engine temp rise a bit faster in the cold. Plus, i need use a simple cardboard radiator block, especially at highway speeds to maintain what heat does develop. The first gen Insight doesn't throw a lot of heat with only 1L in very cold condtions.