In my experience there are a number of factors as to whether an appeal will work.
1. The actual place it's in. Some are bigger bastards than others. Some are actually quite common sensicle, whereas other just want the money.
2. How far you take it. If you take it to the nth degree, some places will just give in, others will let u spend a fortune in expenses in fighting it.
3. Forget about the cost doubling etc. If you show that you're appealing then that process shouldn't apply. You have a legitimate claim (it would seem) so on that basis, to charge double shouldn't apply. If you go to the personal hearing, and lose, then you should only have to pay the original fee.
But at some stage you will have to decide how much the fine is, and how much you will spend fighting it, and whether it's worth it. It's not a criminal conviction, and you don't get points on your licence, so thats for you to decide.
Not long ago I got my dad off a ticket for parking in a non disabled bay, although he showed his blue badge. Apparently blue badge holders had to park in the disabled spaces, or pay to park in the regular spaces. The disabled spaces had all gone so he just parked in the bay nearest the disabled bays showing his blue badge, although he didn't know about that rule because he was a visitor to the area. We got it revoked anyway.
You might want to also say about the hardship it will entail, should that be a factor.
Another top tip, get one of those leather/leatherette blue badge holders. That way the badge will always be displayed correctly. You could even mention that in the letter to prove that it won't happen again.
Good luck.
