Jane - hope you get it sorted out, I'm afraid I'm no expert about whether their advice is realistic though.
I feel like I'm getting back into things again after Edinburgh, this morning I did a 12 mile run and it actually almost felt good, until now my longer runs have felt far more of a struggle than they used to, but I might finally have recovered enough to get going again.
I'm kind of making up my own programme this time - for my first mara (Berlin 2006) I followed a programme a bit too strictly and overdid it when I should have listened to my legs a bit more, and finished in 4:51. For my second (Edinburgh) I made it up myself, increasing my long runs like most of the other schedules, but fitting other runs in depending on how I felt, what my club had planned, etc etc, and it worked a lot better - I took nearly an hour off my Berlin time and finished in 3:52. So this time I'll be following the same approach I think. I look at plans to get ideas of the sort of sessions I could fit in, but I don't feel like I'm tied to them if something else crops us.