Hi Colin,

Though you've not mentioned which model year cars you mean, the answer is likely to be the same: not easily. It really does depend on how wide the boosters and rear-facing seat are, but personal experience suggests that this will not be easy to do in these cars. The Avensis is wider with a usefully larger back seat, so that might have a chance. 

Only way to know for certain is to bring your child seats along with you to fit into a car you are thinking of buying.