In reply to mountainbagger:
Your plan seems fine, although it does depend on how battered, or not, you feel since the marathon.
If you feel ok, you can simply consider your last marathon as a training run.
If I was in your position, which I have been a few times, then make sure you have two or three solid consecutive days of this week.
Next week, just get some shorter recovery runs in with perhaps one perkier, but short interval session mid week, just keep some spring in your legs.
Like you say, you won't improve your fitness in this time, but if you can arrive at the start line feeling relatively fresh and with a bit of spring in your legs that will stand you in good stead.
Best of luck.