John lewis have started to occasionally (shock horror) discount Apple stuff, over the past few years. Even if they are not discounting, the two year warranty is better than Apple’s. And I think it is fair to say, JL have as good a reputation as it gets when it comes to honouring warranties, should the need arise.
One thing to be careful of, Apple sometimes make subtle changes and updates to hardware, that can make it hard to distinguish an ‘old’ model from ‘current’. I have found JL to be selling these ‘old’ models, at least with iMacs if not iPads. I think it is accidental as the genuine current models are also genuinely discounted, but it pays to make doubly and triply certain that the item they are selling is identical version to the Apple Store.
With any Apple kit, I’d suggest buying a device that’s recently launched, even if it costs more. That improves the chances that subsequent releases of iOS in years to come, will still be supported. Nothing is set in concrete and ongoing support can be discontinued, but can also very good, our iPad Mini 2 was purchased in December 2013 just a couple of weeks after launch, and still runs latest iOS.