It's prolly what happens when you buy cheap pikey crap and expect it to
function like a proper shower

Electric showers - spawn of the devil

What would you suggest then? I have been able to find very few mixer
showers that can accomodate exposed pipework down the wall (the shower
has to go on a working chimney breast so recessing the pipes probably
won't be a good idea). Most common mixer units now seem to have fallen
into the 'recessed flat and fashionable' status.