I am upgrading to a 10mm cable and changing the pullcord for a switch outside the door for a new electric shower. I am getting someone in to do the connections at switch and CU but as its a small job i want to have everything he needs here ready. I am running the cable from CU cupboard to the new proposed switch and fitting a dry-lining box into the wall outside the door for it but can i site the box at the level of existing switchs which is 145cm from finished floor or does it need to be lower? any other preparations advice welcome, i.e. will a standard dryling box be deep enough for this or would a deep one be better?