Why can they not build the new London hub in the Olympic park? They will have no use for that land after July and it already has excellent train, tube and DLR connections and the Channel Tunnel rail link. Plus I think the number 25 runs there from Oxford Street. And it already has a bus link to STN.
I just checked on google maps, they could extend the runways straight up Hackney Marshes and tunnel the A12 under them a bit like CDG