The first two volumes should be available directly from Sheva. They have been improving their act re distributors in the UK and elsewhere and an "official" release through distributors should be imminent. By the way, Sheva is now, at least technically, a British label - it transferred its registered offices to London about a year ago.
As the pianist thereof, I hope the project will be as rewarding to hear as it was to do. There are pieces here equal to anything by British composers of the time.
Thanks for this information.