There are plans to develop Lower Marsh and link it to Waterloo Station, also The Cut is being 'up-marketed' all the time (if you call chainstores an improvement!) But there is lots of traffic around there from local residents, media offices and the Old Vic. There are already some lovely pubs, cafes and restaurants but alway room for more good food!
Maybe talk to the TAS people - their restaurant on Borough Hiogh Street was so successful they opened up a take away off shoot.
They are a chain (with 3 outlets) but hardly on the Wetherspoon scale. Also, I often walk past a half empty Slug and Lettuce on BHStreet when the small local pubs are jammed - Ive wondered how successful this branch is - maybe the local developers can be convinced of another policy.
Phil and Jonathan ... I think you are Gong to have to set up a mobile establishment at this rate ... a different location each night, with your itinerary posted on here so we know where to find you ... saw a lovely airstream for sale the other day ...