Something else to bear in mind is that you can't take non-folding bikes on the Overground during the Olympics regardless of the time of day. They've kept that rather quiet so far but I saw it listed on one of the GetAheadoftheGames pages.

I'd thought about cycling from Stratford back towards Whitechapel and then skipping onto the Overground rather than fighting my way across Tower Bridge but it's a no-go.