I am really out of my depth now, sorry about this.
I took a back up before I started the process of updating my map. Since I am struggling with the map upgrade I decided just to throw the backup back on the device (so at least we would have a usable GPS) but low and behold, I get the message that there is not enough space on the device to receive the backed up files. I appreciate that you are likely sick of my mumblings but is there any explanation why I cannot restore the backed up files?