It's difficult to write about ghosts and I think you've done an excellent job with them.
Thank you :-) It did indeed seem quite tricky to communicate the sense of 'what it means to be a ghost' without making the characters too 2-dimenional, so I'm really pleased that you think it worked here.
I do wonder who the next set of house ghosts are going to be. Fred Weasley might be a good choice for Gryffindor.
Yes, perhaps! The thing about ghosts, I think, is that they have to have 'unfinished business' in the mortal realm, and not be ready to move on. It would be a shame for Fred if he felt like that, but I agree - believeable.