I can't give you any specifics - I don't even ride a Brooks - but I can tell you that I've ridden three saddles on my current bike, and every change has completely changed the way I fit/sit on the bike - even though tilt, height at the top of the saddle and nominal fore/aft placement didn't change. Stem changes, moving the hoods around, tilting the bars, the whole shebang - even from the Specialized Lithia to the nearly identical but firmer Jett.
If your sitbones, your knees and your lower legs are happy, I wouldn't change the fore/aft position of the saddle. What that does is change the relationship of your knees to the pedals. If you want to adjust the reach, put on a shorter stem (or, counterintuitively, sometimes a longer stem can take pressure off your shoulders as well).
Speed comes from what you put behind you. - Judi Ketteler