EditedHere is the GSV overview of the roads in and around the hospital.I assume you came into the site from here: -
https://maps.app.goo.gl/FoyVdoccZc4RyneF7The photos on the PCN show you clearly driving past the Buses Only signs. Looking at the map, I would think this bus gate is there to stop people rat-running around the large roundabout on the A125. Did you not know what the blue signs meant or what ? The car park you seem to have been trying to get to, is not a hospital car park, but a council one: -
https://maps.app.goo.gl/WVzGnv5ugxxQw2Bx5Note that as well as the Buses Only signs, there is also a No Left Turn sign facing you as you come up to the T-junction.
Basically as they have re-offered the discount, this may be your best option, because the contravention seems to be made out, and adjudicators cannot consider compassionate grounds, (which comes under mitigation).
Sorry if the above isn't what you wanted to hear, but it is the reality of driving today, especially in and around London. I looked for a sign about the fact the road is not a through route, and there are these signs: -
https://maps.app.goo.gl/j14FLnPAufosrfXy7However, I suspect this didn't register as you merely wanted the car park, and were not a "rat-runner"
There is, of course, the PCN and whether it contains any errors that could render it void. I haven't looke at it yet.Hopefully others have run a magnifying glass over it while I have been typing this post!
EditThe PCN seems to be OK.