With these kinds of issues it's very much about your approach to good housekeeping and,
dare I say it, health and safety. Legally there's no recourse against you if you haven't
PAT tested but if something happens - let's just say an electrical fire - at the studio,
you could end up with all sorts of people coming in to inspect / investigate the cause of
the fire etc. If they discover you haven't been PAT testing, that'll tell them you've got
a slightly slack approach to H+S and they might crawl all over you. If you demonstrate
that you do take these kinds of issues seriously it'll put you in a much better position.