On my occasional visits to Manchester Airport, I always visit the enthusiasts' shop on the ground floor of Terminal 1 . Over the years, the number and variety of charts has diminished and on my last visit, I asked the person in charge of the shop about this and, apparently, the person who supplied the charts is no longer at Manchester.
Regarding your enquiry about the Oceanic boundary points, if you google "Shanwick " , you should get some information which may assist you.
Incidentally, it would be interesting to know from individuals employed in the avaition industry if, with the introduction of electronic flight bags etc, paper charts are already starting to disappear from the flight deck.