"Disabled parking rip off"

I recently took my elderly Mother for a Frimley appointment at Aldershot Centre for Health. My Mother can only walk a few steps and needs to use a wheelchair which I brought with us. She has a blue disabled badge and I had been told that I could park there free of charge, as at Frimley Park. Unfortunately my sat nav sent me into a nearby housing estate and I arrived in the dark, slightly late for our 4.40pm appointment, so rushed into the clinic in rather a panic as we had waited over 3 months for the appointment and I didn't want to be turned away. I had intended to double check the parking arrangements on arrival, but forgot in the rush. I have now received a fine from P Smart Parking. I'm not happy and will be refusing Frimley appointments at Aldershot in future.