Take the Tube from Heathrow to the city, Picadilly Line. All day all zone ticket is 6GBPs, to destination only is about 3, many other options available, but not as easy to use as MetroCard in NY. Another quirky thing is you have to run your ticket through the gate on exiting the station. If you lose your ticket its a 20 GBP fine or so the signs warn. You buy the ticket from an automated machine or a booth, just like in NY, though you have to give destination which could get complicated, consult the map.