Files copied right after completing a backup?
 

I ran SD, then booted into the backup, then ran DW and Disk Utility, then booted back into my main machine and ran SD again (should have done the above steps first!!) and 50M of files were copied?

Is this normal? It strikes me as quite odd that there were that many differences right after doing a backup.

The system is constantly busy/changing, Ed, so having files copied when you booted from the system isn't unusual at all.