We got the Infa Comfy cruiser(which took over from the trek 8 is my memory serves me correctly). It's an alternative to the SNS... and I like it a bit better. It's smaller width wise, but fits taller children and as a booster has the highest safety rating (that's what the tests say!!! Don't shoot me SNS lovers! hahahaha). Once DD has outgrown her seat, we will buy another comfy cruiser for her.

Have a look at the sites posted. It gets a tad confusing, I know now I'll have to brush up on the rules with the harnesses again...

Good luck!
Oh this is another question I was meaning to ask... how do I find out what their safety ratings are and what they compare like with other seats... I am so a first time mum

What's SNS? and convertible booster? Eeek So confusing lol.