A £10 kettle you might expect to last no more than a year, however even this could be argued, whereas a £200.00 item you would expect at least a couple of years etc.
There is not a defined time for any item, but the length of time an item you would expect to work properly is generally determined by the intial price of that item.
No warranty or guarantee is relevant to your claim.
Your contract of sale is with the retailer so dont let them fob you off with 'contact the manufacturer' or 'sorry its out of guarantee'.
If you have a valid claim, then the retailer has a legal obligation to deal with it for you, otherwise get to the Small Claims Court.
Retailers know this and are likely to deal with it as soon as you show your understanding of their responsibility, they wouldnt want to bother with going to SCC where they are likely to lose and incur added penalties.