When I tried to upgrade my system to the latest Ubuntu version the checks for free space failed – I needed to free up more space.
I did not have enough free space in the OS partition but had lots on another partition.
Ubuntu downloads new versions of programs to a cache area :- /var/cache/apt/archives
All you need to do is to move this to another filesystem with enough free space and then link to it.
sudo mv archives /newfilesytem
sudo ln -s /newfilesystem/archives
Now your Ubuntu upgrade should have enough free space