Irish,
reading your posts, I think you are spot on in the accuracy department. If you're shooting approximately an inch at 15 yards, you should be able to shoot a 1.75" group at 25 yards - theoretically. I don't think that your solid 15 yard fundamentals disappear just because you're a little farther away from the target.
Are you using the same size target / point to aim at? You may just be very comfy with the sight picture at 15 yards and the smaller appearing target at 25 may make your sight movement in the wobble zone more noticeable. E.g., for 10 yard practice, I usually use a 1" sticky dot, but at 25 yards I switch to a 6 o' clock hold on a 3" round sticky. That let's me keep the same accuracy at various distances. Try a target size that lets you stay in a wobble zone you are comfortable with and see whether your group is more in line with the 10-15 yard group.
One gentleman here recommended getting an SW617 and practicing at various distances - that'd be perfect to get accustomed to varying sizes of targets. With that 617 you can shoot out to 200 yards - with significant holdover - and practice on the cheap.