"Disabled Parking Charge"

I visited the Health Centre for an appointment. I immediately looked for a disabled parking bay and left my vehicle unaware that there was any parking fee applicable. 12 days later I receive a Parking Charge Notice from a company called Smart Parking demanding £100 (reduced to £60 if I paid within 14 days). I have started an appeal process but am concerned that if my appeal fails I will be liable for the full amount. Seems totally unfair on two counts: 1. Charging for disabled parking at a hospital facility and 2. Not being able to appeal without incurring a higher penalty charge.

Would appreciate any comments from the NHS department concerned.