I have a Triton Rapide 4 shower. It has started leaking quite badly from a little overflow pipe at the back of the unit and when I lift the actual shower head and lead off its holder, I hear a 'gurgling' noise coming from the unit and more water pours out the overflow Can it be fixed? If so what is it and is it a big job - I am quite good at DIY, but is this a complicated thing to fix ?...or should I just keep away from the July sales and buy a whole new shower instead.?!! Many thanks Jenny