Well, it seems as though the radiotherapy has worked as well as we could have hoped. His nose is still scabby, but it's pretty much back to the shape and size it was before, so even if the tumour hasn't been eliminated (we won't know that for a few months yet) it's definitely been shrunk a great deal.
He's still low on energy from the radiation, but his sense of taste has started to come back and his mouth isn't sore any more, to the point where he can eat fairly warm food again. He's even been out in the garden planting sprouts this week.
Thank you all once again for all your good thoughts. It means so much to us.