Just by typing "Airing Cupboard" in Yahoo search box, I got two sites so named. The first was used as name for place to to leave messages about one's gripes. The second involved building a louver ventilated clothing storage space.

After seeing wow's post below, I went back and looked at the pictures taken of the process of building the airing cupboard, and could see no wiring to provide warmth, which actually could be hard to make safe, nor any way of forcing air through it. Things would be packed so tightly I would be concerned that mildew could develop.