Hi DJA, there is implied good news (you must surely have used TCD at least once for this puzzle) : that your back has recovered.
I know nothing at all of the theme, though thanks to the internet I'm learning. The extra letters make 2 words (7,5) which don't really give me any clue as to what to do next. The 2 words might refer to anywhere between Maine and Florida, or just about anywhere in Asia.
Working through the 12 names from jumbles, I've found 11 of them in a list of characters of a work by the unclued name. But no John (from 12A).
As to the location, would I be right in thinking that it must be somewhere along a line which used to have the scheduled service ?