depends how long you are planning to stay, if i am staying one day I usually rent a car, which is much more comfortable, and faster, which means I can catch a flight back home on the same day and that way save some time and money on accomodation. I once took a bus from EMA to LHR and apart from taking me 3 hours it costed me 30 pounds (one way). never again. you can arrange a small car for even 25 pounds, plus around 15 pounds of fuel for the round trip. and it will take you to drive from STN or LHR less than 2 hours if there isnīt much traffic, and that way you also have some wheels to get around EMA.