Douglas Maus! Welcome back - nice to see you have a friend
I survived Loch Ness - it was tough, but I gritted my teeth and kept going, struggled on through thick and thin. That was the 10k - I believe some nutters were running a marathon too
Marie - it does have to be the exact certificate on the Paris website. Some doctors will do it for free, especially if you're running for charity, or for a charge of about £20-30. It doesn't have to be your GP though, so if you know of any friendly doctors...
It is possible to run a marathon with pf. Can you get the physio to tape it up for you, even if that's a few days in advance? Definitely worth having the tape in place as much as you can between now and the race.
I ran the Paris marathon with pf - stood on the start line with a metro ticket in my pocket and promised myself I'd pull out if it got too bad. Up till about half way it was sore, but not impossible, then after that everything else started to hurt too so I stopped noticing it. I got to the finish I and I don't think it did any lasting damage.