Interesting that you used the phrase 'not designed to run more...' I suffered a stress-fracture a couple of years ago and the consultant I saw at the hospital was absolutely useless and suggested that maybe I wasn't designed for running and should just stop...needless to say I now use that for motivation!
Doctors' see that an aliment is caused by something so their advice is usually to stop doing it. Sometimes this is correct, sometimes it is simplistic and unnecessary!
Vicky: makes sense, same weekend as my marathon. Have a few mates who've done Dublin - supposed to be a decent one to do with not too many hills or anything nasty. Isn't recovery this week on the 18/55mi schedule for those dates? hopefully as I'm in recovery mode this week!!
Fear not, I've got a spare week in the bag in case of sickness/accidental excessive partying etc
Think I'll be doing HMs for the first two (mostly because I signed up for them thinking the tune up races were 8miles to 15miles not kms ... well done me, but think I may have gone this route anyway if I'd engaged my brain!) and put the long runs into the mid-week, possibly shortening them. For the last one I'll do a 10km race.