The Mole Valley Line runs between London Waterloo and Dorking, with a branch off to Chessington South on the way. This branch would be included with the route, bringing the total mileage in at around 28 miles. Stock Class 377/6 (looks similar to a class 377) Class 450 Class 455 Class 456 Class 707
I would buy anything with South West Trains/SWR in it, though I would prefer London to Reading with the Windsor and Circle Lines.