Ive learnt from another of my posting that I need to use winscp (or similar program) to transfer my files across, so I consider this resolved. However if anyone knows if usb transfer will be on the cards for a future release please let me know
When you insert a USB flash drive XBMC should auto mount it, just where it's mounted to can vary depending on your distro.
Just pop in your USB flash drive and then login to your Pi via a remote ssh connection.
Use the mount command this should give you the mount point for your USB flash drive (/dev/sda1..sda2 etc) and access to your media files.