Thanks for the replies. I was hunting for info by googling around but they mostly lead to the usual suspects - Naval-tech.com, fas, Global security etc.
About the Americans, there's some pretty good stuff available on the direction they are going.
This site
http://www.nrl.navy.mil/content.php?P=04REVIEW177
seems to suggest thst they're working on using Fiber Optic hydrophones in their next generation systems. That was already implemented on the WAA on the Virginia class subs and the newer TB-33 Towed array will use the same kind of hydrophones. (I believe the existing sonars around the world use PeizoElectric hydrophones. Just getting a basic grasp of what that meant-had to relearn some of my high school Physics)
Another good site -
http://www.navlog.org/TB29.html talking about the TB-29A - basically a lower cost version of the TB-29 because it uses COTS technology. I keep hearing the term ARCI which I'm assuming has something to do with COTS.
I have a question about the Combat Control systems on submarines - BSY-1 and 2, SUBTICS, the new system on the Astutes... What exactly do they do? Are they just really advanced data processors for the sonars or do they do more (target localization/TMA and weapons guidance)?