As an alternative to repair or buying another � you could try asking for a repair/replacement from where you purchased it, even though it is outside their guarantee period.
Under the UK sale of goods act � goods have to be of merchantable quality. In simple terms, they should last a reasonable period. What constitutes a reasonable period depends on the type of goods in question. You cannot expect a disposable cigarette lighter to last a year, but it would be reasonable for a �1,000 flat screen TV to last 5 years (or more). It would also be reasonable for a microwave to last 5 years, however if the seller chooses to refuse a refund � your only option is to pursue a claim through the small claims court. Which to be honest, is not worth the hassle, unless the value of the goods is at least �100.
Personally, I don�t know why an organisation like Which? doesn�t support a few high profile cases against retailers, insisting on 5 years as a reasonable guarantee period for durable goods sold in the UK, and destroy the lucrative rip-off extended guarantees sold by retailers.