156 Climate control

Hello!

How are we all? Good!

Can anyone shed any light on this for me?

The other day, my 156 started blowing hot air very enthusiastically at
me while driving, with the air controls set as follows:
Temp:20
Air qty: Auto
Other knob: Demist/feet.

Since then, it will only give me a hot air- as if the sensors feel that
the temperature in the cabin is very cold, even when the temp selector
is turned all the way to the left.

I have tried the procedure for putting the cc in 'manual' mode and back
from the handbook, to no avail. The only thing that I can govern is the
amount of hot air (using the middle knob) that I get.

Other info that may be useful:
Alfa 156, 2000, 1,8TS.
Also, the water temperature gauge has been gradually showing a
progressively lower temp (now stabilises around 1/4 of the gauge) for
the last few months. May be associated with the same problem, possibly not?

I am in Wilmslow, Cheshire, the local dealer, Mangoletsi, is a bit of a
trek, but they seem OK. Could anyone give me a clue as to what might be
going on, perhaps it's something I can fix myself, how much it's likely
to cost?

By the way, is there another option for Alfa repairs near here?

All advice greatly received!

Charlie