I agree. As long as the temperature is comfortable I am not going to spend a fortune on diagnostics and repairs. The windows (all of them) do seem to mist up badly if I get in and my clothes are wet (or moist) but other than that I see no obvious signs of damp. Carpets, including the boot, feel dry and there are no unpleasant smells. I've experienced damp problems in two of my previous cars and it was decidedly grim after a while. 
The problem may be one of three things (that I can think of at present):
There may be a small leak which means the A/C system has to work harder to achieve the desired temperature when in cooling mode, hence why the 'Eco' mode light and console display isn't illuminated/shown;
The control system for A/C system and/or Eco mode is faulty so its always on 'full'. This may include faulty temperature sensors, wiring, physical controls of the A/C and ventilation components or some part of the computer-controlled system (hardware or software);
A fault with the display - less likely given the light and the LCD screen are both affected.
Not sure what would be the most likely cause, and difficult to track down, even at the dealership. I would caution against getting a re-gas unless absolutely necessary (if you can't get any cooling or it doesn't cool enough). The reasoning behind this is that the wonderful EU, in its infinite wisdom, has decreed that all cars from now onwards shall be filled (new or regassed) with the refrigerant gas R1234a, which was
supposed to be more resistant to leakages (less escaping into the atmosphere and polluting/causing global warming), but in reality is less resistant to leakages. Even though legal refrigerant gases such as R410a and R134a are available to replace the same in our cars, I think they aren't allowed, its only in the construction industry that they are. If you do go (at some point) for a re-gas, check with the dealership/garage what can be offered - if you can (legally) get the direct replacement using the original gas, my advice is to do so.
Sometimes the lack of usage of an A/C system, especially in winter months, can lead to the oils in the pipework drying up (they are circulated when the system operates to keep the components in good nick) which can lead to reductions in system performance and even failures. As other have said, if you have climate controlled A/C, leave it on all year and just adjust the desired temperature to suit the time of year for your comfort level, leaving it on auto mode as much as possible.
Also, in winter, once a month (preferably once a week) run the A/C on full cold (min. temp possible, e.g. 16degC) after the car internal temperature has reached its normal level (say 20-21degC) for about 5 mins, to circulate the oils when its in cooling mode; similarly in summer, do the same for the heating function on its highest temperature setting (29degC), which should kill off most of the bacteria that can grow on the inside of the air ducts in wamer, humid conditions and cause that damp, musty smell and is a contributory factory in respiratory problems. Doing so can be a bit of a phaff and uncomfortable, but is worth it if it means your car's A/C system lasts as long as the rest of the car.