Hiya cheekystar.
Is it really bad? THink I'd take all of the clothes out of the robe and give it a wipe with a mold removing spray (make sure you check the label to see if' it's suitable for the wardrobe). Being a real Monica Geller wannabe, I often just wipe the inside of my wardrobes with those antibacterial wipes to keep them fresh!
Then I think I'd leave the doors open and turn on the radiators to let them dry. When you put your clothes back in, could you leave the door ajar to keep at room temp? Also how about leaving a dehumidifier in the room? You may be able to purchase small non electrical type ones for cupboards...