Seeing as its barley a year old, I don't see how they can really contest the durability of the item, assuming the microwave has not been abused I think and reasonable person would expect it to last more than 12 months before it failed.
This might be a better way of getting your point across, relevant parts highlighted:
Source:
http://sogahub.tradingstandards.gov.uk/sogaexplained
Your responsibilities as a retailer
Your contract with the customer
Under the Sale of Goods Act, when you sell something to a customer you have an agreement or contract with them.
A customer has legal rights if the goods they purchased do not conform to contract (are faulty). The Act says that to conform to contract goods should
match their description
by law everything that is said about the product must not be misleading - whether this is said by a sales assistant, or written on the packaging, in-store, on advertising materials or in a catalogue
be of satisfactory quality
quality of goods includes
- appearance and finish
- freedom from minor defects (such as marks or holes)
- safe to use
- in good working order
- durability
be fit for purpose
if a customer says - or when it should be obvious to the retailer - that an item is wanted for a particular purpose , even if it is a purpose the item is not usually supplied for, and the retailer agrees the item is suitable, or does not say it is not fit for that purpose, then it has to be reasonably fit.
If you disagree with the customer about a particular purpose, you should make this clear, perhaps on the sales receipt, to protect yourself against future claims.
Your responsibilities for the goods you sell
You are responsible for the goods you sell and if a customer returns an item they purchased from you that is faulty (it does not conform to contract) because it
does not match the description
is not of satisfactory quality
is not fit for purpose .
you (not the manufacturer or supplier) are legally obliged to resolve the matter with the customer at any time for up to six years from the date of purchase, or in Scotland for up to five years from the discovery of the problem.
Any refund, repair or replacement you arrange with your customer relating to faulty goods must not cause them too much inconvenience and you will have to pay for other costs, for example, collection or delivery.
If you disagree with a customer's claim, you can ask if they are willing for you to send the item to a third party or the manufacturer for inspection. If the customer agrees you can do this, it is important to remember that the goods must not be damaged during this process.
Customers' rights remain the same whether the retailer is acting as an agent or principal.
Your customer also has a responsibility to make sure that they service the item they buy from you correctly and follow any user instructions provided.
Statements about the goods you sell
Anything that is stated about the items you sell - by you, manufacturers, importers or producers - for example, in advertising or labelling, should be factually correct.
It is important that you know what is being said about the goods you sell because these statements form part of your contract with your customer. For example, if an advert says that a pair of shoes is waterproof and a customer wears the shoes and finds they are not waterproof, then the item does not match the description .
There are occasional exceptions to this, for example, if the advert was published and then corrected in public before the item was sold. Other examples are if, for good reason, you are not aware of the statement that has been made, or that the consumer could not have been influenced by the statement.