Right, a bit of an update on this one. Orange offered me a replacement frame gratis and my choice of colour, although not the updated model (not bothered about that). They disputed that it was covered under warranty but acknowledged that the wording on their website was not clear that it didn’t cover demo bikes and that it would be updated.
It took 3 weeks for the frame to come back, having been told that it would take 2 weeks and [because I’d sent them the entire bike, as requested] it came back without my headset or seatclamp – they’d been replaced with other, cheaper makes! My seatclamp did arrive the post a couple of days later, but I’m still waiting on the headset after I asked them for it (and got no reply to my email).
I’ve also asked them on 3 separate occasions what warranty I will get with the replacement but have yet to get any sort of reply.
So warranty replacement frame = good; no reply on replacement warranty, and keeping my stuff = bad (so far).