I've just been reading on another Bird forum, not the RSPB, that the Little Bittern has been breeding and nesting again at Ham Wall this year according to some one who has visited their this year, although there's been no official announcement by the RSPB as of yet.
Ian, The RSPB won't announce this until they are happy that any disturbance is no longer an issue. According to Bird Forum they have announced something but like you I haven't seen anything yet. I was lucky enough to see one male in late May but on mentioning it to the volunteer on the site he wouldn't comment and I don't blame him at all.