I tried to do as you said but it's still not working. The issue is always "retrieving directory listings". I tried connecting with FileZilla from a different computer (Mac instead of Windows) and from a different internet network (my home instead of my workplace) and it's working. Unfortunately my internet connection is extremely slow so the upload will take several days from here. This is why I would need to do it from my workplace (University of Nottingham). I have also tried to load the files using my workplace's computer but connecting it to my phone (as hotspot) and it worked!
Until before the maintenance of the usegalaxy.org site the upload with FileZilla was working. Is it possible that some change tat was made is now not being recognised by the network and so the connection is being blocked? Could this have something to do with the port used?
Do you know how I can solve this issue?
Many thanks for your help,