If you are signed up with Bristol can't they possibly help you any further. As probably you are aware they are very helpful!
Why are you wanting to duplicate the Bristol notes with some more from Oxford? Lets face it they cover the same topics for the same exam. Don't bother. Certain things may be explained differently and perhaps different topics in different amounts of depth. If I was you I would opt for more specalist books on the market which go deeper than that required for the JAA ATPL. These specalist books are not intended to be read from cover to cover, just dip in and select what you want to know about such as tachos etc.