the fishy smell is what happens when you dont wash your crotch enough!!, no seriously the fishy smell is what happens when electrics get hot, overloading and the such like.
post a pic up so i can see what you are talking about and from there i will try to give you a better idea as to what is happening?
what size is the shower in Kilo watts?
from that we can check the cable sizing and the fuse rating to see if the wrong size has been installed.
as for things getting hot, it is a shower after all and cold water is not nice to shower in!! no seriously again, they take an awfull amount of load when running, all sorts of factors have to factored in like the temp of the room, if it is a 9kw shower, its drawing 3 times as much as your kettle when thats boiling!! so its going to get warm a bit.
hope this helps
richie