Sales Of Goods Act 1979.
If goods are not as described/not of a satisfactory quality/not fit for purpose made known at the time of sale by you or the seller, you may be entitled to a repair/replacement or in certain instances to reject the goods and request a refund/partial refund; this will depend on individual circumstances.
A trader may wish to obtain a written opinion from an independent expert to establish whether a returned item is indeed faulty or not, to ensure that the appropriate offer of redress is made to the consumer - it shall however, not be legally binding unless both parties agree to it.
