I am wondering if we could visit Winsor Castle as early as possible, return to Paddington station and then locate the closest spot to pick up the Hop On Hop Off bus pass. From what I understand, you can only get the tickets at set locations and only on the day you actually plan to use it. Correct?
If we had a couple of houses use of the bus, it would probably be enough for us. We would stay on it or just switch buses where the bus routes intersect.