I don't know but I've always wondered if you convert your books to .MOBI and add them to the Kindle4PC app then you might be able to sync those books as well, and I'm sure all of it is legal.
I don't think you need to worry, since they ARE your books. Just grab hold of a converter and you'll be reading before it's September 4th (

) I don't know about UK laws but hey its YOUR book and you do as you damn well please by removing the DRM