i am looking for a cotbed with mattress to buy.

try the links on the left hand side of the page to thinkbaby's shopping partners.
also worth a look on ebay both new and used.
if buying a used cotbed its best to buy a new mattress.
if you can stretch to it buy a spring and foam mattress as in cotbeds it will be used for longer and with a heavier child than a normal cot.
also useful is one with a removable cover.

Hiya Nadine - just brought one from Toys R Us - 1/2 price at £99.99, i also brought the mattress with a removable cover as above for £69.99. Got free delivery and they even rang and gave me a delivery slot - really good customer service.
Maddie xx