Hi Paul, I hadn't tried downloading, just did to see if I get the same issue as you do, it's been on a message saying Initializing Download for a few minutes now, nothing is happening. I definitely don't have disk space problems and the world can't be larger than a few megabytes, only started last night and we didn't explore much.
Edit : 10 minutes later still stuck on initializing download, only thing I could do was quit out of the game.
Indeed mine has also just started working. No resource pack change needed.