Having trouble finding suitable seat for tall 4 year old nearly outgrown her Britax isofix Duo Plus - anyone have a Peugeot 807 and a high backed booster seat? It needs to go in the third row seats as have a 1 year old in an isofix and will have a baby soon in a seat belt held rear facing seat and we couldn't do up the seat belts with three seats across the back.