1. Upload music files from my PC (as a playlist)
2. Play (stream) the playlist on a Android phone
3. Download as a playlist onto my android phone (eg. to play in the car)
4. Download individual files onto my android phone
5. Simple (for someone else, I'm actually quite clever, me)
6. (For free)
Such a thing? Google drive almost does it, but doesn't seem to have a playlist option, unless I'm missing it.