I understand better now. So you are looking for something in a width between the B17 and the B68?
Stay away from the 'S' models if you have trouble feeling too far forward- they are all 'short' and have short rails (which for some reason Brooks thinks is ideal as a womens' saddle, but many of us riders disagree). I think that if you have a smaller bike then it's even more important to have long rails so your saddle doesn't wind up bumping into the handlebars!
I had a B17S(short rails), which I could not adjust back far enough. Changed to the B17 (long rails) which i was able to move further back, rode that for a year and liked, but found my sitbones were really a little too wide for it and were partially riding on the saddle frame. So then I changed to the B68 on both my bikes and have been happy ever since. I keep them shoved all the way back and wouldn't even mind yet another 1/2" back if it were possible.