There is nothing like the spooky disappearance of racers/marshalls. I spent a good 5 km in a trail race this year genuinely in fear that I had run the wrong way.
No running for me today - but I did organise an aquathlon. It has given me a good insight into the effort people must go through for mass participation races. I was more nervous before this event than for most of my races!
Dave, my suggestion would be to search around for another marathon in a few weeks time (if there are any), enter that, spend the weekend resting then start preparing for your new A race. Abingdon will be there again next year.