Triton Hawaii II electric shower

Hi I have a 6 year old Triton Hawaii shower which has started leaking .I have had a look and it seems to be coming from the stabiliser valve.I understand that it is possible to get a replacement rubber valve seal and I was wondering which is the best/easiest way to get at it to replace-any help mucho appreciated

 

yeah your probably right koolpc-they're still selling them in Argos for 49.99