Can I return it as not fit for purpose?

[FlamingoBingo]

I hope someone can help!

I bought a lovely organic cotton filled roll-up mattress for camping with and we used it for the first time last week for half a night, when my DD1 got sick and we abandoned camp after just a couple of hours of lying on it. Used it for three nights this week (tues/wed/thur) and it was really, really uncomfortable. My hips and thighs are still feeling very bruised and tender today - they hurt that much that, as an ex-nurse, I actually think I am suffering the early stages of pressure sores, which would undoubtedly develop further if I were to sleep on it for a long time .

Where do I stand with returning it? It's not a cheap item (£90 I paid) so I can't really afford to replace it as it is, but I also cannot take it camping again. Surely it's not fit for purpose if you actually suffer physical harm from sleeping on it (as opposed to it just being a bit uncomfortable, which I would accept as a 'side-effect' of camping, and an annoyance that I'd obviously chosen the wrong mattress).

I would attempt to return it as not fit for purpose, and state that you are in the medical profession and mention the sores etc.
There is no guarantee that they will refund you, but you can try - you may be lucky and land a sympathetic sales assistant.
Where did you buy it from? If it was online, write a dated letter and keep a copy.
I always find that if you are polite and reasonable when you complain, then you usually receive the same treatment in return!