OP -- I just read your thread and it seems most of the replies, as I believe you highlighted earlier, are from people across the pond and needlessly unhelpful.
I do wish I could assist you in terms of law but I can only express my support for what is an interesting and important question. It is also very nice to see a fellow citizen challenging a seemingly unjust situation through reason. Law and public policy quite often gets things wrong and every nation needs its people to aggressively challenge and highlight the faults.
I have been thinking about this question myself, and it seemed odd to me that I had to pay Apple to insure my iPhone against hardware defects for last 12 months of 24 month contract. It should be highlighted that not all phones have such minimum warranty period which is a product of competitive pressure. Warranty period is usually >= contract period. Surely, one would reason that the phone should work for the complete period of 24 months, especially for a product with premium pricing.
Also as a consumer, I don't know the distribution of faults in the period between 13-24 months. For all we know, it may be quite high so essentially your total cost ends up monthly fee * 24 + subsidised cost of handset + cost for replacement headset (or repair). Of course it is not advertised that there is a X probability of such payout. Alternatively, you can buy an option to protect yourself before the end of month 12. In either case, there is hidden cost, in my opinion, that is not entirely apparent. More importantly, would this really happen if it was not for Apple's pricing power.
Anyway, I interned, long time ago, as a policy advisor in the Consumer and Competition Policy group at Department for Business, and there were definitely teams that looked into complaints of similar nature -- since I didn't work in this area; sorry I can't be of much help. It may be worth giving a call to one of these: Department for Business, Office of Fair Trading (remember colleagues directing people of them) and Ofcom (not sure about this one).