You'd need to do a lot of research to avoid a jarring note - no table service in pubs, for example. Also, very few of them left in central London - you'd have to go to one of the "rough" areas in the East End or other inner-city places. Also, they tend to be noisy - you can't hear yourself think. Which might offer comic potential.

Somehwere painfully touristy like the statue of Eros at Piccadilly Circus?