Amazon have just dropped their price for this by £10. The next best price seems to be £49.99 from Play.
"This really is the ultimate answer to Life, the Universe and Everything - all five radio series of The Hitchhiker's Guide to the Galaxy collected together for the first time, in a handsome box with magnetic lid. From the original Primary and Secondary Phases, through to the more recent Tertiary, Quandary and Quintessential Phases. Also included is an exclusive bonus disc containing two programmes from the BBC Archive: Kaleidoscope from 1980 (going behind the scenes of the second series) and Six Characters in Search of an Answer: Arthur Dent from 2002."
14 CDs in total. Duration: 14 hrs 45 mins.