There's 4 flying clubs at Southend, so the prices tend to remain competitive, (in no particular order);
Seawing Flying Club
Southend Flying Club
Southend School of Flying
Willowair Flying Club
I recall that they each have at least one C152 on strength.
Suggests you visit them and get some quotes, and more importantly whether you like the feel of the club and its instructors/facilities/ambience etc.
4