Britax Adventure Group 2-3 Car Seat (Billy)
Side Impact Protection with deep, softly padded side wings
Seat shape correctly positions lap belt over the child's pelvis
Seat belt guide correctly positions diagonal belt over the child's shoulder
Easily accessible seat belt path
Height adjustable headrest helps support a sleeping child
I paid £80 for this seat 18 months ago ... have just picked up another one for sproglet #2 for £24 delivered. Nice and easy to use, comfortable for my son. I believe this seat may no longer be made by Britax.
It is not ISO fixing, it uses a seatbelt.
Only minor flaw is that after repeated use, the removable seat cover can unlatch. Easy to apply a permanent fix with a blob of hot-glue.