When i turn the HW tap on the boiler bangs with a nice gas explosion inside it, sometimes it even blows its own flame out!! so far its showing 3 faults on the diagnostic button- firstly it read fault A8 (programmer lead) then next time- E2 (CH flow NTC defective) now its saying A7(hot water NTC sensor or connecting lead) surely it cant be all 3 all of a sudden? anyone got any other experience with similar problems?