I know some people don't like CeX, but I think this is a great deal. Play have these for £149 and HMV have them for £199.
This works out at less than £10 a season and Redmption is included too (although Redemption is the single disc version).
48 Disc Set
A revolutionary show in terms of both form and content upon its debut in 2001, 24 has been hooking more and more viewers ever since with its thrilling, multifaceted plotlines that never fail to surprise. Kiefer Sutherland plays Jack Bauer, the head of the Los Angeles Counter Terrorist Unit, and each series plays itself out in real time, with every hour-long episode representing an hour in one very eventful day in Jack's life. This collection features the first seven series in their entirety. The series' spin-off feature-length film REDEMPTION is also included.