Just getting the cabling through for this into the bathroom . The cable on the mirror is quite short . How will an electrician connect this to the feed cable I’ve put through ? . Does he require a recess socket box behind the mirror ? . Presumably he just connects with a terminal block in the recess ? 

When I fitted ours I just put a shallow back box in the wall behind the mirror, recessed more than normal so that a flex outlet plate could be set back a bit and not hit the back of the mirror.  T&E runs to the box and plate and the flex from the mirror is terminated and secured by the plate.

 

Something like this: https://www.screwfix.com/p/lap-25a-unswitched-flex-outlet-plate-white-with-colour-matched-inserts/89178

12 minutes ago, Jeremy Harris said:

When I fitted ours I just put a shallow back box in the wall behind the mirror, recessed more than normal so that a flex outlet plate could be set back a bit and not hit the back of the mirror.  T&E runs to the box and plate and the flex from the mirror is terminated and secured by the plate.

 

Something like this: https://www.screwfix.com/p/lap-25a-unswitched-flex-outlet-plate-white-with-colour-matched-inserts/89178

That’s great for the ensuite as it has a false stud wall . Bathroom is an issue . Bathroom mirror goes straight against plasterboard wall of the room next to it I.e no depth . So I can’t recess a box behind it . There is ‘space’ above the mirror but not for a socket . A terminal block could be ‘pushed’ up there - is that allowed ?

2 minutes ago, pocster said:

That’s great for the ensuite as it has a false stud wall . Bathroom is an issue . Bathroom mirror goes straight against plasterboard wall of the room next to it I.e no depth . So I can’t recess a box behind it . There is ‘space’ above the mirror but not for a socket . A terminal block could be ‘pushed’ up there - is that allowed ?

 

You can just use a Wago box, with some 222s: https://www.screwfix.com/p/wagobox-junction-box/7355f

Photo to make it clearer .

1 minute ago, Jeremy Harris said:

 

You can just use a Wago box, with some 222s: https://www.screwfix.com/p/wagobox-junction-box/7355f

Right ! That’ll do . I was just worried what’s ‘allowed’ and what isn’t . Didn’t want my sparky having a fit ! ?

The important bit is really whether or not the connections are accessible or not.  If connections are going to be permanently hidden away inside structure, then they need to be maintenance-free connections, if not, then ordinary interconnections, like screw terminals, can be used.  Screw-type terminations aren't classed as maintenance-free, so cannot be buried inside stuff, unless there's some sort of access cover to get at them for inspection and test.

 

Wago connectors are classed as being maintenance-free, as they don't use screws, so are OK for use in places like this, as long as they are enclosed in a suitable box, with cable strain relief.  FWIW, I pretty much exclusively use Wago connectors, mainly as they are just so quick and easy to use.  Being maintenance-free is just a bonus.