Just setting up all the wiring ready to have a dual fuel towel rail installed when I have a new CU. The element will be wired into a switch and timer in a cupboard next to the bathroom. Have a metal pattress box recessed in the wall next to the towel rail and a hole through to a box in the cupboard that has a T&E feed from the timer and isolation switch.
Am I okay to drill a 20mm hole into the front of a blank box cover and fit a cable gland and run the flex through the wall to a connection block in the box in the cupboard? This lets me leave the flex longer than using a flex outlet plate and I'd rather not have connections in a box next to the radiator as it will probably have wet stuff hanging over it.
does the metal box in the bathroom wall have to be earthed even though wire just passes through it?