For me this doesn't work. The songs will, after chosing the "remove from downloads" option, no longer be shown as available offline, but even after restarting the phone twice or more times, the space is not shown as free. Any ideas?
One new information - now that I have deleted quite a few albums and downloaded less new albums afterwards, the storage seems to be partially set free over time. That is I get about 10MB more everytime I check, not a lot. It's a little weird.
You'd think that with all the complaints I see about this dating back to 2014, that Spotify would have come up with a less tedious way to remove those unwanted downloaded tracks. Guess they don't care as long as they're still raking in the money.