Thought I'd start a thread for fellow tight-fisted iPhone purchasers not wanting to pay the full RRP 
So far I've discovered the following offers:
1. Carphonewarehouse.com: £20 off. Free delivery.
2. O2.co.uk Shop: £35 off. Free delivery.
Both discounts obtainable via Quidco.com. Possibly only once you've activated an O2 contract, so unlockers might not get the cashback. I'm guessing with this though.
So far I've discovered the following offers:
1. Carphonewarehouse.com: £20 off. Free delivery.
2. O2.co.uk Shop: £35 off. Free delivery.
Both discounts obtainable via Quidco.com. Possibly only once you've activated an O2 contract, so unlockers might not get the cashback. I'm guessing with this though.