John Lewis are also a good option to buy Macs (or anything, really) from if you're in the UK. On, I think, all electrical goods, definitely including Macs, you get a two-year warranty (ie. double Apple's).
John Lewis are also very nice to talk to on the phone, in my experience - I ordered some flowers through them recently for next day delivery, which unfortunately they were unable to fulfil: they phoned me to apologise and the guy said to me, "I really am so sorry about this, it's a dratted nuisance!" The day after, they sent a much larger bunch of flowers than I'd originally ordered.
In the UK, all goods must be "fit for purpose" and must be fixed or replaced if they break within a reasonable time frame. For things you'd expect to be of reasonable quality, this is usually 6 years (if your £5 Argos blender breaks after 5 years then it's probably not covered, if your Apple laptop breaks after 4 years then it really should be).
John Lewis are also very nice to talk to on the phone, in my experience - I ordered some flowers through them recently for next day delivery, which unfortunately they were unable to fulfil: they phoned me to apologise and the guy said to me, "I really am so sorry about this, it's a dratted nuisance!" The day after, they sent a much larger bunch of flowers than I'd originally ordered.