We have decided to spend a week in Cornwall in early October. Our goal is to stay in a small locale, and have quiet time with some sight-seeing. But we're running into a couple of issues. First, we don't want to drive, so we're limited in a couple of ways. Either we stay put in a place with enough to do, such as walks on the coast and countryside, choices for pubs and cafes, or other sights. With these features, we wouldn't mind staying put for a quiet week without needing transportation other than walking. Or, we could stay in a larger place on a rail line (St. Ives, Penzance, etc.) which could afford us the chance to take day trips to nearby places. Unfortunately it seems that the rather comprehensive bus service in Cornwall ends in mid-September, making it hard to get to or from the villages which are so popular in summer. So the question is, where would you recommend we stay in Cornwall in October, if we weren't to rent a car? Or is it just not reasonable to tour Cornwall in October without a car?
Sounds like you've done good research on the transportation options, even though the results weren't what you had hoped. Have you tried visiting the websites and/or Facebook pages of towns you're considering? Personally I can imagine greatly enjoying either a "staycation" or a rail-oriented tour, provided you choose place(s) to stay that fit your taste.
This site may give you some ideas.
http://www.allaboutcornwall.com/Events_Cornwall/What's_On_October_Cornwall.php
And here's an article about visiting Cornwall in midwinter
http://www.telegraph.co.uk/travel/destinations/europe/united-kingdom/england/cornwall/articles/cornwall-in-winter-what-to-see-and-do/