That sub plate isn't compliant with the TSRGD2002 for use with that sign (unless they have a departure from the DfT, which I bet they haven't). I work as a street lighting and signage engineer in Hertfordshire. Non compliant signage means 0% chance of enforcement. That particular sign is almost always covered with an "except for access" caveat which usually renders the sign next to useless.
Happy to double check this in my books Monday if it will help?
Last edited by Oranoco; Oct 30, 2015 at 05:12 PM.