In message , Martin Rich
writes
You should be able to get a ticket which is both a one-week 6-zone
card and also a season ticket from Leatherhad, and should be able to
buy this from a national rail (not London Underground) ticket office

This is by far the best option, especially if you want to leave
Leatherhead early in the morning. It's simply a 7-day "Leatherhead to
London Season ticket, with underground".

Buy it at the Leatherhead ticket office (but not in the Monday morning
rush hour, they can be forward dated). You'll probably need a passport
photo so you can be issued with a National Rail photocard, which they
can do when you buy the ticket.
--
Roland Perry