Hi Boo,
My son is 2yrs 8mths

and we recently got him the Britax Evolva 123 Ultra which can last until they are 11yrs old!! Anyway we think this seat is great, starts out as a 5 point point harness then a car seat with normal seat belt then a booster cushion, would def recommend it

Good Luck
Jd_mummy xxx
PS You can buy in places like Halfords but we found ours cheaper on line looking through compare websites...