You are not alone....
See the other post on the Opal 2 shower problems on How To Mend It .COM at:
http://www.google.co.uk/search?q=triton+opal+2+%22low+pressure%22&hl=en&prmd=fd&tbas=0
The problems seem to be either the pressure microswitch or the power supply voltages - both can be fixed for under a few pounds, but may require soldering. Don't forget there are dangerous voltages inside your shower if it is switched on at the external shower switch, even if it is not running.
Malc
November 2010