No mortgage outstanding, but I still insure the buildings. I don't see the insurance thing as an issue. The rewiring was done at least to the then current standards at the time. A few bits are still in imperial multi-strand cable not metric solid core but the sizing is all adequate. Everything is polarity-correct and there's complete earth continuity, and all metalwork that should be bonded is bonded. All insulation is PVC, nothing braided cotton or rubber coated, which are known to deteriorate over time. I've added a few bits since then, but using the same switchgear (100% Wylex) and cable, so no-one except me knows exactly the order of installation. Given my conservative approach to loading cables and the fact I fuse some circuits lower than I could going on the cable ratings, the possibility of a wiring-related fire is remote in the extreme, because the fuses would blow before any cables could dangerously overheat.
I do the same thing with appliances and extension leads (which do easily overheat if loaded heavily whilst coiled up). Most electricals will come new with a 13A plug fuse apart from things like table lamps. All my stuff is fused at the lowest rating that it will reliably work at without nuisance blowing, so I have replaced a number of 13A plug fuses with 10A or 5A ones. The basics of electrical safety is you want the smallest fuse closest to the appliance to blow first, so any overload is applied to the shortest length of cable. If nothing you plug in to a socket can pass enough current to overload the circuit cables you won't have any problems.