I wish we'd gone for spring to be honest. We got a foam one and have to turn it twice a week ebcause dd (9m) leave a great big dent in it where she's been sleeping. Need to get her a new on soon I think.
I can't remember what we bought, but did a google and this is off the babyworld site.
For the sake of hygiene always buy a new mattress for a new baby
Have the internal dimensions of your cot to hand when you go shopping; mattresses must be a snug fit in the cot to avoid the baby getting his head or another part of his body trapped in the gap. The gap between the cot and the edge of the mattress should be no more than 4cm
Check that the mattress isnt too deep: the distance between the top of the mattress and the top of the cot should be a minimum of 50cm when the cots mattress base is in the lowest position and a minimum of 20cm when the base is in the highest position
Think about the content of the mattress - if theres a family history of allergy you may opt for a simple foam one. Most of the well known brands offer good quality foam mattresses; dont be tempted to buy a cheaper, unbranded mattress or you may find it dents after just a few months use. If you want a mattress thats more supportive as your baby grows, you might choose a sprung interior mattress with foam padding
What is the mattress covered with? PVC will be easy to clean, but will not absorb heat and moisture. Some mattresses now have wipe clean, breathable covers which dont encourage perspiration
How easy is it to keep clean? Some foam mattresses have ventilated sections which are good for keeping your baby cool and dry, but can collect milky dribbles which make them difficult to clean. Look for removable sections which can be washed
Some manufacturers now make mattresses with two ventilated sections: one at the head and one half way down, so that when a small baby is tucked into the cot in the Feet to Foot position, his head is still over a ventilated area
First time we got a Mamas ands Papas coir one which was very flat after 2 years of use and ds wasn't especially big.
2nd time got a Mothercare striped sprung one which was cheaper but fared much better despite being used longer. Still as springy but didn't get the more expensive one with removeable cover so as dd was a sicky baby it is a bit marked.