as an after thought ......jenw was right ....where are you going exactley as getting into london during the games from croydon would be a right old pile of jams .....it is now and its not even games month
www.laterooms.com Plenty on their old chap. east london probably cheaper than west but you can tube it anyway I use the site all the time and they are pretty good, you'll be able to find some £50 quid bargains on there!
I regularly use www.booking.com to find hotels. You can specify number. Of. Rooms, size of party, nights you want and it finds loads of hotels rated by price and customer reviews. Hotel costs vary so much with demand it is a really quick way to find somewhere good and good value. I have used it for London with good results before. It works across Europe too. I do a couple of motorbike trips each year (Assen this weekend being one) and we found great places in Bruge and near Assen this way.
If you wake up in a room on the top floor kitted out with mahoosive B&O tvs etc, antique furniture and a bathroom big enough for an orgy: panic.