For North London, I suggest sticking to the Northen Lines or Piccadilly Lines if you are looking for traffic from public trasnsport: King's Cross, Islington, Archway even Highgate and Mill Hill. Islington was a gold mine for me a few weeks back; I used a private apartment for three days from Booking dot com site. Romford has a reputation with some for dodgy clients and timewasters, but I only did two days at a popular chain on South Street. I was low volume and only saw five guys in total over the two days. It was fine for me and I met two possible regulars that are willing to drive to where I usually base myself in NW London.