Would be interested to know the answer to this. Am tempted to cancel my Apple order and order one through CPW, but it's only possible for me if it can be delivered over the weekend.
From the CPW website:
"Free next day delivery (Order before 5pm)
Saturday delivery is £7.50
Youll receive a 1hr time slot on the morning of your delivery. If it doesnt suit you, just text or email to reschedule"
So not sure, maybe it will come anyway, but to be sure you should phone them and ask.
Just phoned them, I was expecting to be on hold for ages but actually got through straight away. My order isn't showing on their system yet (even though I've got confirmation email), they said right now it can take up to a couple of hours but if I call back later and before 5:00pm then they should be able to change it to Saturday delivery (charging me £7.50).
I just worked my way through the online order process again (http://www.carphonewarehouse.com/buy/APPLE_IPHONE_5S_64GB?stop_mobiyes&portal=AWIN&promo=87027) and still can't see anywhere to select a Saturday delivery option.