This Question of the Month, concerning airing cupboards, is answered by ETCI:
Question: Are there special requirements relating to electrical equipment in airing cupboards?
Answer: Yes, because of the temperatures and low humidity in an airing cupboard timbers tend to dry out and become more flammable. The electrics in an airing cupboard should be limited to those items mentioned in the Wiring Rules such as the wiring to the immersion group. Preferably, switches should be mounted outside the airing cupboard but where this is not possible or desirable they can be installed within the cupboard provided certain precautions are taken as outlined in the Wiring Rules. Because of the daily use and frequent and rough usage in an airing cupboard the electrical installation tends to deteriorate quickly and it should be examined regularly to ensure that there is no damage to the cabling and switches etc. which might cause a fire. (Answered by ETCI)