Sorry, but none of the points you have made about signs are valid. Motorists are under a duty to look out for and obey traffic signs. The sign is clear, and in a well lit area. Clearways don't need to have red lines, just signs at regular intervals.
HOwever, with just this one sign, I think the council could be considered to not have put in adequate signage to indicate the restriction. This is a very busy, indeed heavily trafficked road with two lanes each way over the bridge, so it would be very easy to miss this one sign, especially with HGV and bus traffic, and there is nothing on the road like double red lines to show there is a restriction.
So I suggest you submit reps on the lines of what you have told us about your regular previous parking here, and not seeing the single sign on the two lane approach over the bridge that tells a motorist it is a Red Route, and make sure you empahsise the absence of red lines which you would expect a Red Route would have. Why call it a Red Route if there is nothing red to indicate No Stopping !
