You'll be on the blue start then. I think all the blue numbers are low, I've had a ballot place twice and my numbers have been low, think it's just how they pick them. Really at the blue start you can just start where you like, there are just poles up that say where the 'pens' are, it's a much smaller start than the red one, I've always started at the back of the blue start and it took about 20 minutes to get to the start line. I had to walk the first time I did it because of a bad injury and by the time I got to mile three where the red and blue starts join there were about 2 others from the blue start with me but they were still streaming out of the red bit, reckon it must take ages to cross the line if you are at the back of the red start!
I don't know anything about osteopaths to be honest, so not sure. It sounds like the fact that you are sitting all day is what is making it worse as I suspect it's tightening up while you are sat still. How often do you get up from your desk to walk about it bit? Do you do your exercises at work, say in your lunch break? How long do you hold each stretch for?
If you were still feeling a niggle it wasn't wise to increase the distance really. Doctors won't really want to know as it's only to do with you running, unless it's affecting your mental health or something. So what advice did the physio give you about stopping it reoccurring? Are you doing any exercises you were given before or after a run?
Maybe see a sports therapist instead of a physio? Mine is great at diagnosing problems; I also get a massage that releases any knotty or tight areas and she'll give me exercises to help with whatever the issue is.
After a two week rest are you going straight back out and doing the mileage you were doing before? Are you stretching properly (2 x 30 second stretches of each stretch when you get back from a run)? Have you been told what the issue is by the physio and been given rehab exercises or instructions?