CAA give away the information for free. All of the aeronautical information is available on the web in the AIP. The base map is not theirs to give away. Copyright belongs to Ordnance Survey and the CAA have to pay royalties for its use.
Electronic charts ARE available. You can get them
here The price reflects the charges they have to pay Ordnance Survey for the licence.
Mike
PS
Even with the CAA giving away the information for nothing there are plenty of examples of errors in the GPS databases being produced from it!
Mike