How to play files downloaded via Firefox?

[NielsM]

Hi all,
After downloading videos in mp4 format via Firefox for iOS (iPad or iPhone - same problem) highlighting the filename gives the option ‚play in VLC‘. However, other than the fact that VLC then opens, nothing happens.

Is there a fix for this? What settings need tweaking?
I note there are no plugins available for iOS that might enable VLC to do this - but maybe someone out there had the same problem?