A: 

This will not change a low pressure shower into a high pressure.

They are cartridges for low and high pressure situations.

Answered 158 days ago | Anonymous

A: There are no servicable parts in this shower and the cartridge must be replaced, it can be ordered online by clicking on the link below.
If it was tiled in without use of the tiling shroud then possibly the tiles are too close to the body to allow access, if so they can be carefully cut away enough for access but still close enough for cover plate to conceal without need for any retiling.

http://www.showerdoc.com/shower-spares/triton/TRITO-83304970-HP-Valve-Cartridge-(Comes-With-Seals)

Answered 8 days ago | Alastair