We did this late last year - DD was very sad to leave her best friend (and her best friend even more so.. I think she took it far worse than DD!) DD is also a child who likes a structure in her life and is not a big fan of change. Her old school was also outstanding.. and her new one, well, less so although it had a new headteacher to improve things.
She surprised us all by settling so quickly into her new school, which she had not had the chance to look around. After her first few days her teacher said it was like she'd always been there.
To compound poor DD's life, we moved her again six months later when the school on our doorstep finally had a place (the other one was a mile up a hill and a few busy roads away - I have two younger DC and I was going quietly mad)
Again, she settled really quickly, made new friends and is really happy. Despite her new school having a high turnover in Y1 teachers due to one leaving and the replacements/supply teachers not hanging around for long. Finally now, in Y2, she has a permanent teacher and I hope the rest of her primary school life will be settled. Not that she seems to care!
She still talks about her old friend occasionally, but she doesn't seem to miss her if you see what I mean. She has written the odd letter to her old class but they have not written back, nor would I expect them to really!!
It's amazing just how resilient children can be. I would not have expected her to cope so well given her personality, but it's been like water off a ducks back. She coped better with the move than I did I think - I was beyond stressed dealing with school entries as DD2 needed to apply for a reception place as well and we had no idea where DD1 would be come September. It all worked out in the end though and they are both happy at the local school.
Obviously all children are different but so long as they have the stability of the family unit and their things around them at their new home so they feel safe, I think that gives most of them the strength to deal with change.
Good luck with the move and getting a good school!