With only one side of the heater warm and the other cold, it is likely to be the heater control arm has come off on the cold side. The guide you have seen on here will help you to fix it but it is a bit of a fiddle.
The radio NCDC 2013 is the correct set for a 2001 3.2 Elite and is the radio model designation, as is the 2015. Both these retain their codes; unless it's been replaced by a replacement set. If there's no radio pass (or the code noted somewhere - check the radio manual!!), VX can only supply the code for the original radio fitted, unless the change and code has been diligently recorded on the VX dealers records, but you obviously need to know which dealer! Otherwise, a good radio specialist should be able to retrieve the code from the radio itself.
As with any car, proper demisting is only possible with an efficient working aircon. People think that aircon is only for summer use, and switch it off when it gets cooler, but then wonder why the car mists up! Worth checking the pollen filter is not clogged as well, and is the right one fitted correctly - early cars had a standard filter, whereas later cars had a carbon filter. If the air con is ok, then damp in the cars interior is the only real other cause - I would check the front nearside scuttle drain is clear (guides on here) and that the passenger carpet is dry. If not, then it is likely water has got from the blocked scuttle, past the heater into the foam insulation under the carpet (again, guides on here how best to dry it out). There are other ways water ingress occurs, all outlined on here, but as many will agree are a pain in the backside.....
The door locking issue will almost definately be the solenoid /motor on the affected door; easy enough to change with the door card removed (guides on here). Cheap enough to buy at a local scrapyard; I have had this issue on several Omegas, and replaced them all with a secondhand ones with no further problems.
Good luck!