to not know whether my 3yo should sit in the front or back of the car?

[TheScience]

I am no car seat expert and do not have any ERF seats etc. I do try to stay within the law of course and want the safest arrangement with the seats we have.

What I'm not sure of though, is when I am transporting 3 under 4s in car seats, is it better to have my 15kg 3.9yo on a booster cushion in the back middle seat, or a HBB in the front?

I hope it goes without saying that if you go for infant carrier in front and older two in the back, you'd use the HBB not the cushion!

I guess newer cars probably do have fuller seats but the law was only changed in 2006. So anyone with an 8 year old or older car is pre this legislation.

Yes that's true bertie. And of course, they dont want to affect the sales of their 7 seaters do they? Why buy a 7 seater for 4 dcs if you can safely fit them in a 5 seater?