Thanks for all your help. I bought the new diaphragm £15.21 inc. VAT and P&P and just fitted. I now have hot water again with just a turn of the tap. took me about an hour, but that was only because the spring flew out and I could not find the push rod LOL :D :D :D :D :D
sounds good to me. Found the part 248734 VALVE-DIFFERENTIAL-DHW for £25.95 is that all i need. What about diaphram? Sorry about all the questions but if I can save a few £££'ssss then it will be much appricated.
That was going to be my next question. Is it something I can do myself. I read through the installation manual and it explains how to replace the diaphram and diverter.