It's a good idea to keep cables that are insulated or sheathed in PVC away
from polystyrene thermal insulation - the two materials have been known to
react and break down the cable covering. It's recommended that the electrical
installation is periodically checked by a competent electrician - preferably
every year - so that you can keep a record and spot the signs of a problem,
before it becomes a potential hazard. [3.4]