The most popular Brooks is the B-17, which is what you appear to have, albeit yours has lacing holes punched in the skirt. Also comes in a narrow version and a short version.

The B-66 is wider and a bit shorter than the B-17 while the Swift, Swallow, and Team Professional are narrower. These are all unsprung saddles.

http://www.wallbike.com/brooks/standardsaddles.html

Since you've been riding on the big cushy gel saddle, my guess is you have an upright riding position.
You may want to consider the sprung saddles.

There's the Champion Flyer and the B-67
http://www.wallbike.com/brooks/singl...ngsaddles.html
The leather will still be rock hard as it should be but the springs will absorb road bumps, etc.

I got a B-17S for my wife's bike but she didn't like it so I use it on my Sprite. She likes her B-68S just fine.