There's also a train from HND to NRT. Two to three per hour. The trip is around two hours. Most needs a connection on the way. The cost, as advertised on the web site of the railway operator -- Keisei -- is 1,560 yen. Much cheaper than 'limousine' buses or Narita Express connections. The train station is on the basement floor at HND and at Narita, it's the regular Keisei station, also on the basement level.