How can i fix the heating element on a Triton Opal 10.5kw?

My Triton Opal 10.5kw chrome design shower tripped out on the main fuse the other day and now when i put it on i have to have it on nearly full heat to get any where near warm, which obviously means it comes out at a lot lower pressure. I wondered if a heating element had partly gone inside or if anybody had any experience of this. Of course the waruntee ran out three months ago.