Posted: 17/08/2016 at 23:38
OK, let's not panic here. You can do the distance, you've proved that. You've got all the transport and accommodation sorted. Even if you go all the way round at a brisk walk you'd probably finish in about 3 hours, so you're going to be able to finish it.
I'd start with picking a day for your long run, and starting with whatever your recent longest run has been, add 10 minutes to it each week. As slow as you like, just build up time on your feet again. If you can get up to 10 miles or more before race day, that would be nice, but it's not crucial.
On other days, just try to get out when you can. One day a week of pushing yourself a bit harder would be good - a short run much faster than your slow run, some intervals with rest breaks in between, or some hills. Gradually adding in another one or two days of comfortable runs would be even better.
Basically, you can get round, and any training you can fit in will help. And if the worst comes to the worst, you spend a few hours walking and jogging around central London on closed roads, and someone gives you a medal at the end