Bistros near the Tower Bridge, London
I don't think you can beat Magdalen . . . it's our favourite place in London at the moment (http://londonfood.typepad.com/stuff/2007/02/market_leader.html). I would give the Garrison a miss (http://londonfood.typepad.com/stuff/2007/05/more_rolls_royc.html). At the south end of Bermondsey Street there's also the Bermondsey Kitchen, which I've had pretty good food at before, not been there for a couple of years though . . . http://www.bermondseykitchen.co.uk/
In London, Vinoteca (http://www.vinoteca.co.uk/) on St John Street is a relatively new and very worthwhile winebar. Not in the exact Tower Bridge vicinity but still City of London near Farringdon tube station.
For Paris and Rome you should post on the international board. I haven't been inspired by eating in Paris for some time now but on a recent trip, I enjoyed Comptoir de L'Odeon in the 6th near to Odeon metro and you can find a good selection of wines, cheeses, pates, terrines at that place amongst other things.