I started a thread about folders a while back when I was thinking about getting one for exactly those reasons. There are certain rides I'd like to do within the NY region that I'd need to get to by either car or train first. A folder would free me up to use a service here in the states called AMTRAK, which allows bikes, but not always "walk-ons" unless they are folders. I almost bought an inexpensive folder just for these trips, but people talked me out of it.
Anyway, I don't want to hijack this thread about touring in England. Back on topic...