My DD is 11 months old, but very light and tall. She is still in her Mamas and Papas baby car seat but I feel she is getting too tall for it as the straps don't come over her shoulders at the top. She is too light for the next stage of car seat. DH went to mothercare yesterday and they recommended a combi seat. Are they any good?
Ideally children should stay rear facing until they are at least 2.6, but really the longer the better. In the UK most 5 point harnesses only go up to 18kg and booster seats only go up to 36kg. In other countries 5 point harnesses go up to 36kg and booster seats go up to 45kg. I would see if any of these will fit your as they have been tested up to 25kg which is approximately 6 years.
There's a non-isofix one called the Be Safe Izi Kid X1 that goes up to 25kg aswell but I can only find the isofix version which seems to only go up to 18kg.
There's also the Akta Graco Cosmic Comfort S but I heard this one is only up to 25kg if used in the passenger seat. If you use it on the back seats it is only up to 18kg. I don't know if that's true for definite though so would be worth checking out just incase.