They are only carrying the shells that are legal but that's enough to get you going.
Helger have both types of CEFX (the new ones are high demand though but apparently easy to drive). They also have the new Parma Zytec and the Speed8, Zytec is easier than the original CEFX to drive.
CML seem to have run out of Proto P35's as they are no longer made, the Speed 12 is not legal but I liked it to drive.
There are several Corally shells but I have not tried them.
I tend to use the LRP additive LRP65010 (replaces6501) from Helger. The club I run at also has a lot of people using CS High Grip - they are both on the list on racechat as legal odourless. LRP seesm to work well on rubber tyres too. Jack the Gripper is supposed to be good but i have never tried it.
Apparently it is best to run whatever most other people are using to get best results, so I would get a supply of the LRP......
Regards
Scott