I have droplets in mine too from the same area which is caused from the AC pipes condensating. (I’ve seen the condensation on the pipes when I dismantle myself). I can assure you it’s not the heater box and the dealers and Ineos don't know the solution because it’s isolated to only some. Everytime I ring them, Ineos are looking into it but they did mention one time, they would open up where the heater box is located and insulate the pipes (hot and cold). I already have a new air box, new cabin filter (as per TSB) and it didn't make any difference and I would not bother.
Insulating the pipes doesn’t get to core reason why it happens in the first place and to only some. The solution I discovered my heater previously was luke warm and apparently you need to have the HVAC at the right dew point. The fix is bleeding the coolant both high and low pressure, top up coolant to max (cold engine) and check again after a few weeks and repeat the process to get rid of all the air in the HVAC. Once the heating is working properly, the pipes will not condensate and drip. Heat should appear on a cold engine within 5 minutes.
So far I have no dripping when I put the demister on but I need to wait for summer and a hot humid day to test thoroughly. So far so good.
In summary, the heater and air con needs to work perfectly to eliminate the condensation.