Not convenient for everyone but the Viewing Park makes no charge if you enter on foot (or with pushbike ??). A half hourly bus service passes through the Cargo Area which is about a five minute walk from the Viewing area.
One has to wonder who dreamt up the £ 12:00 charge given the straightened times we are told that we now live in. Perhaps they are trying deter people from visiting in cars?
Planemike