What could this be?

After advice on another thread I was about to start and ease of with my pace BUT before I did I have picked up an injury.
I have been running around 50 miles a week aiming toward a sub 1:30 at the GNR, training was going well although I was aware I was probably running my easy runs to fast.
I was away last weekend and knew I would not be able to run for 3 days so I did my normal weekly mileage in 4 days which included a Temp 8 miles at 6:50 pace and 13 miles the following day (my last run). This I guess has caused the injury or it could be coincidence
Currently I have not ran for 6 days (tried 5 miles Wednesday-thinking I maybe could run it off) and cannot see myself been able to run any time soon, I have a physiotherapist appointment on Wednesday.
My questions are:
The pain I am having is in my right leg mainly outside of the ankle and up to the inside of my knee, it also continues less severe up to my gluteal area. A strange pain over a wide area closet pain I can associate it to a sprained ankle but over a much wider area? Any ideas I can usually work out what I have injured and take the appropriate action but this has me stuck.
ALSO how much is the time off going to cost me in relationship to my GNR time (in 4 weeks)-I ran a time trial in training a couple of weeks ago at just under 1:35 a hilly course and felt could have gone a bit faster in the first ½. And a 8 mile tempo @6:50, so think I was on course for a good chance of under 1:30 BUT now no running for a week and could be a lot longer-how much does each week without running reduce race time?
I have swam a few times this week to try to maintain the cardio, 2.5k this morning very boring and apart from aching shoulders did not feel anywhere close to the effort of a good run, may try my bike later but am worried that will aggravate the injury.
ADVICE WOULD BE MOST WELCOME PLEASE, THANKS A P!$$*D OF RUNNER

Any chance it's coming from your sciatic nerve, if it's all the way up to your gluteal area? If so, it's gluteal and piriformis stretches and exercises for you - unless it's actually from your back... I did my piriformis in with some fast running three weeks before a marathon. Took several physio sessions and lots of stretching but I ran the marathon.

Yeh DB I wondered if the sciatic nerve is involved, I have tried using a foam roller on the ITB just incase will also roll the gluteal area. Thanks for your reply

How did the time off due to your injury effect your marathon time?

You don't need a foam roller you need a tennis ball! Lie down, bend your left leg, put your right foot up just in front of your left knee (so your right knee is sticking out to the side). Put a tennis ball under your right buttock, move slightly until you feel where it hurts - now stay there for a while, then roll it a bit, find another sore spot, repeat. You can Google to find the good stretches for piriformis syndrome.

Re. marathon, I don't know how much it affected my time; probably not a lot. Basically my taper was slightly longer and rather more extreme than intended - the physio let me do a short run the Wednesday before the race but otherwise (except for a very painful three mile hobble before I went to the physio) no running for three weeks.. It was my first marathon and I was aiming for under 3.45. However, this was Greater Manchester Marathon - very cold (5 C before windchill), raining and hailing, and we were running into a gale for the second half, with legs seriously stiffening in the cold, so I wasn't too disapointed with my time of 3.47.