Don't know if it helps, but my mum bought a ventilated foam one when she had me, and it lasted through my sister and my brother as well! The only reason she's not using it when my lo is born is because it's too old!

I'm going to buy ventilated foam
http://www.johnlewis.com/230232735/Product.aspx
Em 16+6 x x x
If the other EmilyB reads this, can I have my username back please?