Discovered this morning the wall switch to the shower wasn't working. After isolating the supply I opened the switch up and discovered that the live terminals looked like they caught fire! the switch the brown and cracked on the live side, the copper wires are black and there is a mark on the wall, so I'm sure steam has got into it. There was a smell aswell when the shower was operating around where the switch was (inside an airing cupboard in the bathroom - surely the electrician who re-wired the place would have fitted a ceiling switch). The wiring in shower unit itself looks fine.
Because of this I would like to move the switch onto the wall outside the bathroom, as it would be easier to move the incoming wire in the cupboard, covering it with the plastic protection trench, and drill through. This would mean adding a new wire from switch to shower (which needs to be done anyway as I'm reluctant to use the same burnt out wire). This I presume would need Building Regulations Part P approval, though myself (and especially my dad if he agrees to help!) are confident in electrical installation.
Would I still need an electrician to carry out (or at least check over) the work, and what type cabling and switch would I need? The shower is an 8.5Kw Neptune Solo.
Also in this cupboard is a wall-mounted switch for an old heating system, which is now home to the rear security light. Do you think I should move this switch aswell?
Many thanks in advance for your help.