The contravention seems made out, but often these things can be overturned on a techicality like the camera not being approved. However, nobody expert on this aspect has posted so far. Bad time what with Whitsun half-term etc so people not being about.
What you could do is submit reps on the basis that you didn't have time to read the closed hours as you passed the sign, there being no advance warning of a timed restriction except the sign itself.