You were either trespassing, because it's not land over which the public has a right to pass, or you were within the scope of the waiting restriction, because it's part of the road.
We're not concerned with the former.
So, would an adjudicator find that this land is part of a road?
Frankly, with no current or historical evidence (in particular GSV) who knows?
My view is that it would be considered to be part of the road.
You could request the council-with their Highway Authority hat on- to provide you with a copy of the highway terrier for the location as this would at least establish whether they maintain the area.