as we had mice , i rewired a house in pyro cable . unusual but above domestic spec . the engineer testing it was amused but saw my point . it should outlast me .
overspec good .... test certificate necessary .and sensible .
i have seen much worse than your old stuff ,the last example had a test cert (a self cert from an approved firm who had employed a cowboy to keep up with demand )
be sensible .ask questions and encourage them to enjoy their work or diy and a skilled first second and third opinion .