Aqualisa Quartz shower problem(?)

[A.Clews]

I've recently noticed that the sound of the pump/processor of my Aqualisa Quartz has changed, from its normal constant "wooooooooo" sound to (most of the time) a gently pulsating "wooo-wooo-wooo-wooo" sound. And last night after my GF had used it, it didn't want to restart (water just came through at 'gravity' pressure) when I went to use it, though after several prods on the start button it did get going. The shower was installed in February 2007.

Has anyone else encountered problems like this, and what had to be done about it?

[Grumps]

I don't know what the problem is, but Aqualisa Quartz showers have a 5 year guarantee (well, mine did back in 2004).

[John]

Could the shower head need descaling? (causing too much back pressure) Try removing it and running it for a while.

[A.Clews]

Thus spake John ( [e-mail]) unto the assembled multitudes:

Unlikely, as I live in a very low limescale area - my kettle for example is still clear of scale after more than a year.

[John]

As a diagnosis stage it is still worth removing the shower head to see if the problem changes