Showers MUST be wired direct to mains input fuse box / consumer unit- and you only need to have a separate fuse / isolater for it
Some say connect to cooker as this has > 45amp fuse but preferrable any spare position on its own should /can be used as long as the fuse matches- isolator / is in line with the requirement on the shower installation paperwork -- please please please make sure the shower is fully earthed and you would be better to have a spark look at finished installation
pc6493
December 2008