Looking to buy a Dorking to Henley on Thames return ticket, flexible, leave around 1015, return around 1730, outward via N Downs line to Reading, return via Central London. Forum ticketing site gives a very reasonable £17.50 (with railcard) flexible return, which according ot BR Fares is any permitted route, but it only seems valid on return journey on Elizabeth line to Farringdon, then via Redhill, itineries via Paddington and Waterloo are more expensive? But doing searches for Dorking to Henley via London both ways give routes via Waterloo and Paddington for £17.50 return. I don't understand what is going on, and what restrictions there are that are not obvious. can anyone clarify please?