Thanks for the tips guys.
so I deleted 60Gb of iPhone video's - who'd a thunk iPhone would make movies? 😱 But I only gained 3GB of space!?!
The new problem is that the deleted files seem to have moved themselves to a backup file - Yes, I emptied the trash. Maybe it'll shift after I've backed up?
Edit: nope, backed up and restarted and it's still the same???