Mira 723 shower, gravity feed

[juco]

Cant find my previos post as the search is nt working for me.

I have now used a service kit and replaced the piston/spindle, however having re assembled this I now find it is leaking at the point idicated (below) but only when the shower is switched on it doesnt appear to leak when switched off. Can you give me any guidance on what to do now? Or what to check for. I am presuming it must be a washer that the water is by passing.
thanks

 

[Breesey]

You need to replace the seal behind the ring with the two key holes in

 

[juco]

Ok still no joy have cleaned and inspected all that I can think of. Breesey if its the washer type seal as opposed to an o-ring then that came with the service kit and has been replaced. I have taken some pics showing how I have put it back together as I now thinking maybe something in the way I have installed it. Also a video clip at the end showing the leaking valve.
I would also add that in the first picture I have not stripped back any further than that as I dont know how to get the plastic part out or the metal piece that the piston pushes into (the part with a little water sitting in it), any ideas?

This shows before the piston inserted and cleaned..

This showing large o-ring at the back..

The piston in place..

Question here.. I take it in the next picture the part that has been added should be screwed up tight?
Also when fitting the `spring` one part fits into the groove on the spindle part and the other on the `pillar & sleeve` with the sleeve having the cut out part fitting into the indent so that the spring has restricted movement?

And finally a clip of `Niagra falls` this is what happens when I turn the valve
With the amount of water coming out I wonder if its my assembly thats wrong! Within the casing as assembled above are there any other moving parts that could have seized? I know the spindle/piston rotates on a thread to control on/off water how does the temperature control work as I cant work out how that is done, should that have a rotating/moving part?

http://s64.photobucket.com/albums/h194/scudo/Junk/?action=view&current=LEAK030.flv