Aqualisa Shower?

the Aqualisa shower which I have has been quite noisey for a couple of months now and last night when my son was using it, he found that when he switched it off it sounded as though water was still running through it, even though there was not any actual water coming through at the time, it was very very noisey. I switched off the mains in the airing cupboard, I did use the shower this morning same problem I had to switch off the mains in the airing cupboard. Do I need a complete new shower or is it the pump or another component which needs replacing?.