I have to say the contravention seems to be made out both by the photo of the sign stating it is for goods vehicle loading only, and also your admission that you essentially "chanced your arm" by parking there.
However, all may not yet be lost, so don't rush to pay !
So can you please post-up a GSV link to the exact location, so we have have a look at the bay and its signs. Once we've seen the location, further advice will be given. Others on here will no doubt also contribute.
