And the area would have to be with in 150mm of the ceiling or directly above the shower.
However tiling around the shower unit is poor workmanship. Electric shower units have quite short lives and often need to be replaced. Invariably the new unit has the connections in somewhat different positions.
Having the wire run in the wall and lose will greatly help the replacement, IME. However there may be issues with the cable and the stud wall's insulation.