Sorry, should have posted this some time ago - obviously too excited at the time, and overcome by the change of stance at Honda UK following pressure from, in particular, RuthieB!
It is possible, with determination and some reinforcement from information gleaned from these chats, to persuade Honda UK to replace the seat covers free of charge.
Like 'RuthieB' mine were replaced in March at the time of my 5th annual service (about 46,000 miles), after various contacts with Honda UK Customer Service.
Thanks to ClubJazz contributors for support and suggestions.
Good luck to those still waiting!