Under the hygiene exemption for distance selling returns, some (but not all) mattress companies state mattresses cannot be returned if the packaging is removed.
This goes against the principle that distance purchasers have the same rights as purchasers in shops, where mattresses can be tried out for comfort.
An EU court ruling said mattresses, like garments, can be unwrapped and returned.
Alasdair Taylor's Answer
I’d be very surprised in the UK courts exempted mattresses from the distance selling rules or came to a different conclusion from the CJEU regarding the application of the hygiene exception – but of course you would need to look carefully at the particular T&Cs of the retailer the particular actions of the buyer to make a judgement with respect to a specific case.