Has London ever heard what BBQ is?

Why would they? It's rubbish.

Tips for eating in London from me (I live there, and I'm vegetarian so I couldn't care less what you think about the meat);
Falafel - always a winner
Indian Food - as above
For traditional British food go to some traditional pubs, not chains. The same goes for drinking beer. If you don't like the beer, try lager - especially Sam Smiths if you can get it (although there is no music in Sam Smiths pubs).