Hello David,
Thanks for the info and possibilities. These all came from David Mellard, I checked some old emails. He expected that what had been sent to me over the last two years was p curta, obtusa, pedunculata and ophioglossa. He also said the obtusa would be flowering now so easier to identify. Dave has a clonal name for most of the tubers he’s sent, ‘mellow spirit’. Not all of them have this name though. So it looks like diplodium obtusum is a winner!