From the research that I've been doing, the sad news is that it appears that hotel rooms (any chain) are going to next to impossible to obtain in London for all of July and August next summer. And what might be available will have tremendously high rates. I've seen a couple of articles that state that almost all hotel rooms have already been snatched up by the big ticket resellers.
I was so excited that I was able to obtain event tickets, now I fear I might have to sleep on a park bench somewhere. I'm praying that it won't be as difficult as it seems to be. I was actually hoping to be able to use rewards points (silly me).....
I would really consider staying anywhere I could take the Eurostar to St. Pancras station and then go to the games. If you could use points, even in France or Belgium, it would be worth the 2 hours to get to London.
You are going to have to be creative, but it might save you a lot of money and could actually be fun. Remember, at least you can relax and sleep if you need to on the train. Many Londoner's commute for at least an hour to and from work everyday.