Thanks everyone. As things stand I'm planning to keep going while I can and ratfink's "whether it be completing a race, making it round the block, or getting out of bed" is where I am with it at the moment. Whatever I can do, I will do.

I'm surprised how little literature there is on this...maybe runners just get it less than others...the most detailed I've found is Jenny Goellnitz's piece here http://runningtimes.com/Article.aspx?ArticleID=12936.

Off out for a run now anyway.
Cheers.