Not sure if this is the right forum but can't see which would be. Anyways I will be getting BT round to move the master socket and I would like to knock out the hole first before they get here to reduce mess and hassle. However I'm not sure which size to recess the hole for? Any BT guys on here know what size the box is? Is it the same as a standard square electrical box i.e. 70mm x 70mm x 25mm Thanks.