The congestion charge is a bit black and white. You were either in the zone or not. And when in the zone you either paid the the charge or you didn't. And if you didn't pay you were either exempt or you weren't.
By your own admission you failed to update your exemption and received a penalty charge and maybe have two more in the post.
The independent adjudicator can't consider mitigation so you probably won't succeed with an appeal to the London Tribunals.
I'd try writing a representation to TFL explaining what happened. Make it clear that this was an honest mistake, could easily happen to anyone, terribly sorry I'll be more careful in the future, I was entitled to the exemption but failed to claim it so there no intent to evade a charge, please use your discretion to cancel the charges. Enclose a copy of your BB. And so on.
Make sure to reference all three PCNs numbers, so you might have to wait a bit. But I suggest you get any such representation delivered to TFL within 14 days beginng with the date of the earliest notice. If you don't have all of the notices then use those that you do have, don't miss the 14 day deadline.
