If it were my house, I'd be perfectly happy to leave the electrical installation as it is, apart from either a like-for-like replacement of the faulty shower or a simple thermostatic mixer if the hot water system supports it, and consider whether the money saved would be more usefully spent on other things that could provide a greater reduction in risk, e.g. a shower mat, fire alarm system, a washing machine and tumble dryer that won't support a fire, a car with better NCAP rating, a non-slip path, a new house, etc.