Hi Edward......welcome to the forums
The compressor is a common fault unfortunately and does cost a lot but worthwhile in the hot weather otherwise you could have bypassed it.
I suppose the pressure is off you from no longer living in London where a hybrid or electric would be the only way forward.
Good to have you onboard!
It does sound like an issue with the head unit and maybe a reboot will resolve it.
I know there are a huge amount of settings in the back end of the subsystems relating to volume and other functions.
Would need to refer to the handbook again for accessing them though