We bought a rather expensive one from Mothercare. Highly recommend it, cotbed matresses will have to last birth to what 4/5 years old type thing so well worth investing in something of quality and not just looking out for the cheapest type thing. Sleeping is so important with newborns and little ones so not the item to be trying to save money on in my opinion. I believe Mothercare, Boots, Mamas & Papas and John Lewis all do really good quality ones although a lot of ladies online swear by Kiddiecare - never personally used them but they seem to get a lot of good reviews and seem cheaper too.