Hi Steve, gutted to see that you won't be doing the marathon, but the fact that you're still heading out to Paris to support the others says so much about you as a person. I look forward to updates on your recovery over the coming weeks!
I can only echo what everyone else has said. The crucial thing I have learned through this whole marathon training process is how important it is to listen to our bodies...even when we really don't want to. Your results in training have been a real inspiration to me and I'm sure to the others on the forum as well. I just want you to do yourself justice when you do run a marathon as opposed to potentially harming yourself long-term when you could have many more running years ahead of you.
Keep your head up, you've got support from everyone no matter what conclusion you come to.
Knee feeling any better? In response to your question, I did recently get myself a Garmin 410 but am still in the process of leaving how to use it properly. Colchester half may now now not happen for me, slight knee niggles myself and this close to Brighton (one month today!) I think I may be better off with a few days rest but we'll see.