Help, Having just removed cover on aqualisa quartz electric shower fitted by builder 12 months ago found water input and electric wiring emerge from unsealed 5cm square hole in tiled stud wall behind shower. Stud is made or regular water resistant plasterboard so once cut will not take much moisture to damage it. I have stuffed void with fibreglass insulation to stop whatever sealant I use from simply filling up the stud wall. Question is should I use silicone or a kind or flexible grout (or something else) to seal the hole and stop any stray water from entering and slowly destroying my stud wall? Can anyone advise on what to use?

is there a rubber gromet in the shower unit itself?

Just silicone the hole but DO NOT silicone the unit to the wall! There is a void behind body of the shower to keep it cool and if you silicone it it can shorten the life of the unit.

The unit should also be in a position so it only gets splashed and not in an area where it is sprayed continously with water

Just had a look at the Quartz, it has a removable service tunnel for the cable entry, just wanted to make sure the builder hadn't made his own cable entry in an unsuitable place.

As Scottley says, just silicone the hole