assuming your mains water pressure is ok I would guess you need a new flow valve. check out showerdoc.com to identify the model of shower and order the right part
andarew
March 2011
if tank fed try cleening out gauze filters in body of shower
ray
February 2011
I can answer this question...
any suggestions on fixing my mira shower it is showing low pressure ?
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix baths and showers.