triton biaritz shower

[scrumpyjack]

this shower won't turn off .It went a bit touch and go a few weeks ago then got better on it's own---now the water won't stop flowing unless the stop valve is turned off.
I've got a list of parts on the website but which bit do I need to replace----
It has got to be a valve of some sort but I would like to get the right one first time
Any help please??

 

[Softus]

So that we're referring to the same information, it would be best if you'd post a link to the web page that you've mentioned.