C230 W203 A/C regulation out - Blows hot air

[braaast]

Hey guys!!

Thank you for this great forum, read plenty of good tips to look after my beloved C230 W203 2.5L!

Got recently an issue with the A/C regulation - I cannot figure where the problem lies..
(My car has the standard dual zone with the 2 knobs - not the digital climatronic one)

Blowing hot air when A/C on (as well as when AUTO is on) even with the dials on minimum setting.

Note: when the dials are on FULL left (passed the click position) the A/C blows cold-ish air (although not as cold as used to)

I had it re-gas by Halfords (so all good according to them but they aren't Merc specialist obvs..)

Possible causes:
-Dual zone control faulty (although both sides aren't working..)
-Cabin sensor faulty (cannot locate it - cannot find drawings on the web for face lift models)

The outside temp sensor is working fine (displaying normal temp - 16C these day.. not 80C like when faulty)
I have a £15 fault reader and had displayed no issues (of course that's not STAR

Any ideas would be greatly appreciates (as well as a good local in London or the south east - I was thinking of TM Motors or doing a trip down to Olly @Prestige Car Service? )

Thanks guys !!
Ollie