Valiant Turbomax 242 Diaphragm problem

[moggers]

Hello, I need some help We have have what seems to be a common issue with our Valiant Turbomax. We have heating but no hot water on demand. If we want hot water we need to turn the heating on and then it works fine.
I've done quite a bit of reading around this subject and feel confident that it is the diaphragm. The micro switch operates fine and the arm doesn't appear broken. I have viewed the great video on uTube [ame="http://www.youtube.com/watch?v=eqonFQmsaPI&feature=player_embedded"]YouTube - Vaillant Turbomax 242 / 282 Boiler Diverter valve[/ame]
This tells me a lot but from the video and looking myself I see that I have the heat exchanger conected to the valve. I imagine that if I undo the 6 screws (making a note of where they come from so I put them back in the same place) the other things bolted on will hold the diverter valve in place and so the question is
"how much do I need to take apart to slip a new diaphragm in?"
Feel free to question my methods etc. We are a youngish family without spare cash so I'd like to get this right
Thanks for any help/advice you can offer me

[wnjswozo]

these can be a pain of a job to fit new diaphram,i would advise you to get a gs plumber out,if you decide to have a go make sure you get a vaillant washer/o ring kit ,as you are aware the cross plate heat exchanger has to come of to get access,need o rings for that,sometimes the rocker arm starts leaking,good luck