If we were talking about a privately owned home, I would just be trying to get the owner to realize that there is a problem and scare him into getting something done: "Look, this wiring is in such a poor state that's it's only a matter of time before it starts a fire" etc.
I'm not sure there's any specific legislation here which would apply in such a case anyway, not that I would want to go down that route if avoidable anyway.
For rented accommodation, the landlord has certain legal responsibilities to maintain things in a safe condition. I wrote a report for the tenants of a place last year in which the wiring was in a very poor state.
Unfortunately, the situation was complicated by the fact that with the landlord's permission the tenant had built a small extension on the rear and added his own wiring for it. It seemed to be largely the the modifications for that new extension which were responsible for the things which were wrong.
