"which includes the three-year guarantee at no extra cost, with an option for three more additional years Added Care with accidental damage cover for £80."
The word "additional" is throwing me off here. Looking at JL's site its free standard 3 year cover, and you can pay £80 to have that 3 years include accidental damage. I don't think it's adding any additional years past the 3?
Correct. You get three years warranty included free. But as with most manufacturer warranties this doesn't include accidental damage. However John Lewis will also cover you for accidental damage over those three years if you give them an extra £80. It's not an additional three years.