Exactly what sorts of things are being stored on user desktops that need to be backed up? If this is important data, you really do not want this stuff being backed up online over the net. Then again, there should not be any important data whatsoever stored on user desktops, it should all be on servers, with secure space allocated to general “available to everyone” areas, department and/or workgroup spaces, and if desired personal spaces.
For offsite storage of backups, I recommend Stacs, if they operate in your area. Media are shipped to their facilities in sealed containers either via courier or picked up and delivered by a representative. You will need to research such a company in your area, they are usually in the Yellow Pages under computers or data storage/archiving.