Parking on Rank

The notice on Barkers Pool taxi rank reads "No waiting mon-sat except taxis", so Sunday the top part of the rank is not a rank as such. We had a private motorist leave his car there and taxis were inconvenienced no end, enough to call the Parking services. A chap came round and pointed at the sign and suggested it's not illegal for anyone to do so and promptly left. If not a rank, it still is a double yellow, but no ticket issued, but since the rank is used all day Sunday by taxis and any parked cars are a real problem, can this be looked into at all please, and the sign changed to make it a 24hr taxi rank.

As far as we are aware in Licensing the rank was a seven day rank, for Taxi only of course, I will endeavour to get a full answer to this as to why the rank is now signed as a six day rank?