Burying shower electrics behind tiles.

Hi,

I am tiling my bathroom, which is currently untiled. There is an existing electric shower on an inside wall that I want to keep. Currently, there is some plastic ducting which runs on the outside of the wall into the ceiling, however, I want to put this behind the new tiles somehow.

I was going to chase the wall out.

My question is, what would you recommend casing the wire in and what is the best thing to fill the cavity with?

Many thanks for your help,
regards
Rich

Its good practise to use pvc oval conduit:

http://www.tlc-direct.co.uk/Main_Index/Conduit_Pvc_Index/Oval_Pvc_Tube_and_Clips/index.html

but its not a requirement.

You could fill the channel with sand and cement then tile straight over.

You cable MUST run in a safe zone
(vertically or horizontally from the shower.
See //www.diynot.com/wiki/electrics:installation_techniques:walls?s=safe zones

Also an RCD is a requisite.