Well it all depends what part of NW London you are in? LCY is on the DLR as London City Airport stop on the King George V branch.
If you plan to drive from NW London to LCY is will take hours and be fairly torturous journey. Those who travel from East London to Heathrow leave 2-3 hours to get there.
BA Cityflyer is a subsidery of BA and isn`t away into BA.