Hi..I have a central heating boiler that recently stopped working..I thought that we had an immersion heater (as a stand by) but I now know we do Not...I have the electrical switch for one close to and inside the airing cupboard which lights up (with red light ) but no wire connecting switch to water tank...I also have an entry point at top of the water tank (blocked off )..will it be possible to have immersion heating element fitted into the water tank as a stand by should the boiler fail again in the future ?..also if possible what is a ball park figure to costs ?...many thanks in advance