Very interesting day, popped the unit to my local EBME department with thoughts of swiftly re labeling the unit 'scrap', he gave a knowing look and 2 mins later had popped the screen off, opened up the main unit and replaced the coin battery.
as if by magic, the unit now works fine with no fault codes, the cost? 2.44 for the battery and a tenner for the labour and brew.

now thats service :-) better than the several hundred I was looking at paying out for a new board. will rebook for full EBME check up and then the unit is ready to go

cheers everyone for your help on this matter