Where goods prove defective or to have been misdescribed within six months of delivery, it's presumed that the problem existed at the time of purchase, unless the seller can prove to the contrary.

If a consumer returns goods very soon after purchase, he/she is entitled to a full refund. If not, a consumer is first and foremost entitled to have goods repaired or replaced, provided this can be done within a reasonable time and without significant inconvenience to the consumer.

If repair and/or replacement of the goods is unreasonable/impossible, then a dissatisfied consumer is entitled to an appropriate price reduction or a refund. Note, however, that this refund may be reduced to take account of wear and tear.

Don't be misled into thinking that you must accept a credit note or prove an action against the manufacturers (such as, under a guarantee). Rights are first and foremost enforceable against the shop.
No refunds

If you see a notice/sign to this effect in a shop be aware that it doesn't affect your statutory rights and remedies as outlined above. A shop can't legally exclude a consumer's right to a full refund in relation to defective or misdescribed goods which are returned promptly after purchase.

In fact, a shop will have committed a criminal offence and should be reported to Trading Standards Department of your local authority. Trading Standards may investigate and, if appropriate, decide to prosecute the offending store.
Practical advice on refunds

* Check goods thoroughly before you buy them.
* Seek redress from the shop immediately you become aware of a problem.