-
I need to measure the wiring but from what I remember it's a chunky one with thick cores.
Is this an easier approach and means less messing with the CU?
yafe-
Not really, that's just a 2 gang 13amp socket with RCD's built in.
@stevo_com covered the process. I'm inclined not to say too much because liability and assumptions but....
The cable you have should be adequately covered by the existing breaker (assumption).
Any 13amp 2 gang outlet attached to that cable would protect the appliance cable with the 13amp fuse in the plug.
It might be difficult to fit the chunky shower cable into the terminals of the 13amp socket.
Maybe someone else can suggest an accessory that would allow you to connect the shower cable to 2.5T&E with a 13 amp fuse to protect the 2.5T&E. Some kind of fused spur or small distribution board might be a possibility.
I'm pretty sure all of this is within the rules regarding sign off but you should really be testing zs to make sure the breaker will operate, insulation resistance and as Stevo pointed out you need to be sure about what you have on that existing shower cable.
It's not something most electricians would do. I guess at worst you would consider it an alteration to a circuit (not a new circuit) and change the breaker to 16amp. Test the zs to ensure the breaker operates, insulation resistance and add a 13amp 2 gang socket. Then it would be safely installed but not notifiable.
A few assumptions in there so bear in mind this is just advice from some rando on the internet, you should have a professional deal with it for all the reasons above etc. etc.
stevo_com
Airhead
That would be notifiable as you are making a change to the CU, but I don't see why it wouldn't be possible. Lower rated MCB (16A) at the CU and double check the cable size. Just because it was running a shower, don't trust that it is correct unless you put it in yourself. As @Airhead said, it would likely need to be 2.5mm2 to be able to safely run power to the sockets without overheating, especially if it's going through/under insulation. You'll likely want to make sure you've gotten rid of any potential switch line to the shower too, lest you end up making that live when wiring up the socket.