Just updating the list of PKD books on sale at amazon, as they appear to be adding a new one each day.
Today, The Penultimate Truth by Philip K. Dick is $1.99 at
amazon US in addition to those below
Valis by Philip K. Dick is $1.99 at
Amazon US, .
A Scanner Darkly
http://www.amazon.com/A-Scanner-Dark.../dp/B005LVR6NC
The Man in the High Castle
http://www.amazon.com/Man-High-Castl.../dp/B005MZN2B2
The Three Stigmata of Palmer Eldritch
http://www.amazon.com/Three-Stigmata.../dp/B005LVR6C8
The Exegesis of Philip K. Dick
http://www.amazon.com/Exegesis-Phili.../dp/B005LVR7DQ
Note: there's also book called "The Best of Philip K. Dick" showing at $1.99 but it's not a real "best of"--it's simply public domain short stories bundled togehter.
These do not appear to be on sale in the UK.