Hi my lad has just got his first car to learn to drive in a 64 plate KA titanium - Great little runaround except the heater is driving me crazy, works really well on full but as soon as you knock the temp down it blows cold air. Not sure if it’s related but the dash temperature only ever shows 69 degrees.

any advice greatly received TIA

Looks like you need to replace your ambient temperature sensor.

It's located in the wing mirror and if you are so inclined, should be an easy repair. But this is likely impacting your climate control as the car is confused about the outside air temp.

In some cars this even impacts other engine management but not in a way that would bring up any codes.

In any event. Repairing this sensor should fix the issue.