That entrance signage is a bit rubbish. POPLA sometimes take some convincing on signage points - when I've won signage cases I've really walked the assessor through the set up, including maps/diagrams, showing the route the driver took, where they parked/stopped, and showing how the signage would not have been prominently displayed.
Are you local enough to get your own photos easily? I note that the Google Street View images are around a year old. Whilst the signage may not have changed, it would be wise to get more recent photos to show this.