Hi. I have only just seen your problem & don't know the full history so I may be covering old ground.
This could prove anoying having replaced such expensive parts already but have you checked any limit or overheat stats. If the overheat stat has gone then your boiler will not fireup. Some boilers wont go at all others may reach as far as brining on the fan but go no further.
Also checking that the sytem pressure is correct for operation or a fault on the system pressure sensor.
Hope this helps
Robin S, August 2008
