You misunderstand the basics there, in the UK you have the right to commence action for breach of contract against the retailer for 6 years, that isn't the same as a warranty and it's up to a court to decide if the contract was breached (unlikely in the case of a phone with wear and tear).
You might want to read up on the Sale of Goods Act 1979 to familiarise yourself with what it actually means.
Well said, and the customer would also have to prove that the fault was there from the start.
Apple are pretty strict on the EU 6 year thing, and they can still refuse to sort a problem out, as per their terms and conditions, and certain guidelines for portable devices, iPhones, etc.