What is wrong with my Triton Opal Shower?

I fitted a Triton Opal 10k shower when i completely re-vamped my bathroom. At first when i used full power button i had to turn the setting down to 5 because the water was too hot, a point where the Low Pressure light came on . So i used the low heat level at a setting of 7-8 and it was fine. Now because the directly fed water is much colder i expected to use the higher setting. But what i now find i have to use the full power button and maximum setting of 10 just to get the water anything like hot which gradually turn to look warm after 2 minutes. The unit seems to be making a low buzzing noise too. Has anybody experienced this problem and can give me any idea's on how to fix this ...or should i just rip it out and start again....expected the unit to last more than 12 months. Any help would be appreciated.