Im sure that some one will be along shortly to tell you that you are free to ignore this notice as it is 'advisory'
For myself if there is a sign I dont stop - even if the sign is black marker on cardboard and has spelling mistakes!
Ignore an 'official' road sign and the worst that will happen is a small fine - ignore an unofficial one put up by a disgruntled local and you could be in a world of bother, flat tyres, spray paint/indelible marker graffiti, eggs, broken windows etc etc.
The chances are great but they do exist
The problem with this country is if someone parks somewhere for a night without problems, the next day they plaster it all over the internet, and the next night there are 12 vans parked up then more and more, until local people get fed up, then the next time they want to park there the no overnight signs have been installed.