Hi Neil
It hard to say if some of them are better than others... It is just a lot of water mixed with a few dry salts. That is why a lot of people make their own ferts (have a look at the tutorial section), with a few euros/pounds you can have fertilizers for years and you can do whatever you need.
If don't want to play around with dry salts, I have used Tropica ferts sometimes. You have Specialised (green one) with macros and just a few micros, and Premium (orange one) which has just micros. If you have a small tank it won't be expensive to use them. In my town a LFS prepares something similar as well as some UKAPS sponsors...
Jordi