Hi Dave It all depends what is required where cost is concerned. With it being in a bathroom, it is classed under building regs Part P as a special location and therefore it is notifiable work to your local building control. Your electrician will do this for you. It will also need a minimum of 10mm cable running from the consumer unit (fusebox) to a pullswitch and from the pullswitch to the shower. The circuit will also need to have RCD protection. All these need to be taken into account when taking on a job like this in order for it to be certified and signed off. All these considerations will significantly bump up the cost if you are starting from scratch. The best thing to look at is in the Cost Guide section on the Rated People website and that will give you a rough idea. Also look at the cost guide for replacing a consumer unit as well if it is required. Hope this helps Regards Dave ADW Domestic Electrical. .