Hi looking at Britax First class & Joie Stages for my nearly 15mth DD who's almost outgrown her maxi cosi carrier..our car is vauxhall corsa 2009 , we have 2 older children who don't use boosters (past height req) just wondering how comfortable having 3 of them in back would be ? I notice there's quite width difference btw the 2 car seats - can anyone comment or advise which seat I should go for ( for erf) ?