....Bear in mind I have 2 cars, and Roomie does not want to keep the ac going unless it's on (older style compressor), so my remark on seals, valves and compressor still applies. But for both cars, including my Mk3 OCtavia vRS, it's the humidity that forces year round use of a/c for me. Neither car is garaged, and if you forget using airco in winter for a while, both would start to feel/smell like a moldy damp sofa after a month or so.
Regarding HVAC coding, I think there are 2 options, "use in humid countries" or "humidity control/" or the like (I think byte 14 x8 and x4), and the other which I found made more difference was byte 13 "compressor on when not cooling" because then obviously it dries out incoming air. I have actually disabled the byte 14 x8 option and switched to x4 which also does something on demisting (don't remember VCDS description exactly, just have my coding noted), for me the byte 13 change made all the difference I needed. Note it does increase fuel consumption, but only in line with what previous Skoda's did, i.e. if the AC is switched on, the compressor keeps the evaporator at near freezing, that's all.