The diaphragm was mentioned by someone who does not know that your boiler does not use one!
The sensor was a fair but misguided suggestion.
A microswitch was probably mentioned by the same person why wrongly thought there was a diaphragm.
You can clean it if you know how or you can replace the plate HE.
You could clean or strain the system or just wait another 3+ years and do the same thing again.
Tony
Thank you.
The plumber just said it was the diverter valve.
The other suggestions I found were from people on this website who were having the same symptoms as me and the problem parts were diaphragms and temp switches. Also regarding you saying the boiler doesn't use a diaphragm,even the manual and other websites are saying there is a diaphragm. Anyway,I'm not here to argue with you.Thank you for your help and once again am I better off cleaning the HE and if so how or just replacing it?
You could clean or strain the system or just wait another 3+ years and do the same thing again.
Please explain.