A: Yes!
If you have problems with an Excel then it's best just to replace the cartridge, however it is probably worth stripping the cartridge out and checking that the inlet filters are clean, before buying a new cartridge.
To replace the cartridge Pre 2003 units
Turn off hot and cold water supply
Pull front temperature knob off The rest of the knob assy. just unclips
Remove 4 screws that hold cartridge into body
Pull old cartridge forward shouldn't be too tight
Set new cartridge for High/Low pressure (instructions with cartridge)
Slip new cartridge into place remember to check that the new seals are all in place (and don't drop out as you push back)
Tighten screws be careful not to over tighten
Refit knobs.
Turn on water and test. (Occasionally you will have to reset the cartridge temperature, instructions with cartridge)
Easy peasy!!!!
Cartridge Mira 903.33 This cartridge supersedes the previous high and low pressure versions
Link to cartridge
http://www.showerdoc.com/shower-spares/mira/MIRA-903-33-Cartridge-Assembly-(Up-To-2003---Black)-Comes-with-seals
Answered 79 days ago | The Doc