Just wanted to reply to this thread, to say a HUGE Thank you to everyone that helped.
I got the car up on a ramp last night to see the old Diverter Valve covered in Oil/Grease so I though this must be a good sign! After fiddling about finding the right tool to get to all 3 bolts I got it off, and it literally fell into pieces as I did so - The Green rubber diaphram was completely shredded and obviously was the fault! I got the new one on nice and easily, and MY GOD what a difference
!!!!!!!! It is like a new car, I can't believe how bad it was.....
Thanks so much guys, I'm going to replace the one on my Octavia tonight too as I'm sure mine is probably on the way out too.
One last question on it, my parents have a 2008 ED30 Golf and I would like to replace theirs too as it's a bit on and off with power. Do any of you know which type of valve that would have on it? Would this same replacement fit?
Thanks so much once again, so glad I joined this forum now!!