Mattress for toddlers bed - how much to spend?

[reren]

Am about to buy a single bed (rather than a toddler bed) which toddler will soon move into - I'm thinking a cheap bed from ikea with a half decent mattress. But how much to spend? I'm thinking you want something reasonably good to support growing body? Looking at John Lewis site it seems you could spend an awful lot on a single mattress - but who knows how many times he'll wet the bed / jump on the bed - dont really want to splash out too much (not to mention can't afford it!). Does 150-200 seem about right (there isnt much on offer that is a lot cheaper than that)?

[alieh]

We bought a very nice and comfy seeming mattress from Baby Mattresses Online. We chose the pocket sprung one with extras like organic cotton cover and it came to 135 including delivery I think.

[Undiscovered]

We got a coco one from Natramat with an additional waterproof cover. Worked great for both cot bed and single, and currently a sale on http://www.naturalmat.co.uk/ and there's a discount code on mumsnet