I would look for something on the DLR route. The Tube and Trains seem to be getting more packed than ever(I have to back track just to get on most mornings now!) Westferry is only 3 stops in and you have the charm of the Narrow Street conservation area one side and the modernity and cleanliness of Canary Wharf the other. Depending on where you find something you'll also have the Jubilee and Elizabeth lines near by or a walk to Limehouse C2C rail line.