OK, so what I have done as I need 3 carseats in the back of my car is... Tehya is in her safe and sound Royale, she has been in this since birth and I think it goes up to 18 kg, 12 kgs rear facing.

As bub will be needing that seat I have recently brought Tehya the Safe and Sound Maxi Rider, this goes from 8kgs (I think) until 26kgs, it can also recline alittle which I like for when she sleeps.

Noah, who is 5 and around 20kgs still needs a booster, so I have bought him the Hipod Barcelona booster seat, you can use the H harness if you want with this or just the normal seat belt.

So, at the moment, I still have Tehya in her Royale until it get's closer to baby time, Noah is behind the drivers seat, Tehya behind the passenger and the baby, when she is born will be in the middle spot. Atleast I think that's what we're doing. Sure is going to be hard to get bub in and out though.

Oh, and in answer to your question, definately a carseat or atleast a booster that resembles one like the Highpod, the best you can get though is the Maxirider. Both the maxi and the highpod Barcelona anchor to the car and can be used with a H harness.