Well as Mike said - I was curious so I took inside the ZFE. It's in a bad way !
I've repaired PCBs in a similar sort of condition in the past, I am hopeful that the damage has been confined to the power supply side as the unit stands almost vertical on the bike. As always with this sort of thing though the risk of voltages tracking across is there and there may already be sensitive components damaged. As Wayne says though - worth a shot and if it works I have a spare ZFE !!
Thanks to everyone on here for their help and input ad I really think it is worth saying that without the assistance of the GS911 from Mike - I doubt I would ever have been able to trace the fault. So thumbs up to the Hexcode team for designing and building it and BMW UK for lending it to me.
Mike - the coffees, cakes and biscuits are definitely on me at the next meet !
G