The Newhaven to Lewes 123 Bus service runs every two hours through the day and is run by Compass Travel, click the link on the right to get the latest timetable
The 132 Bus Service runs from Newhaven to Lewes on a Sunday and is called the Towns and Downs Wanderer. It is run by CTLA and although it does not have a stop at Southease listed the bus can be flagged down at the Bus stop on the C7 if you use the Piddinghoe bus time plus a few minutes. There is only one bus in the morning and one back in the afternoon.
CTLA also run a Dial-a-ride service that is pre-bookable and runs between 9am and 3pm Monday to Friday in Lewes and the surrounding villages. This service is for people who have trouble accessing other services. You have to be a member and can register for free