Just outside the main gate and almost on the large roundabout ( next to MacD`s ) there is a bus stop in Rochford Road. Its about a 3 min walk from the terminal. Buses numbered 7 and 8 ( and a few more ) will all take you into Southend, and from there its a 2 min walk to the Mud ( sorry sand ).
Buses are every 15 - 30 mins depending on the day. :0