Flow valve replacement

[goofy gorilla]

Hi I've got a bristan frenzy thermoststic bar shower, had it installed about 4 years ago THIS
One here..trouble is turning it on is very stiff, also design is so silly, very smooth, when hands are wet very difficult to turn on. I'm thinking of replacing the control valve in it..ref 5+6 in spare parts..in link..is it easy to replace? Ta

 

[undertrained]

Should be easy enough to replace, but you might want to remove the old one and try it removed first, it could be debris, or something else.

 

[goofy gorilla]

Thanks I'll remove the old one...try and clean it up ..wd40 ?..thought bristan products were top quality?..not impressed