is the phone on contract? Because surely it's reasonable to assume that the phone will work for the length of the deal? "Sales of Goods Act" could come into play.
Interesting idea.
The issue is that the iPhone is treated differently as far as repairs by the networks. The customer goes directly to Apple for warranty service rather than via the provider, and Apple are not the retailer in this instance.
iPhone hardware issues are a pain in the bum for business contracts. At work for a faulty iPhone we have to book a Genius Bar slot and send one of the lads to the local apple store which takes at least a couple of hours. Anything else we just phone the provider and they send out a courier to pick it up. The turnaround is a bit longer but it only takes 10 minutes to arrange.