If the AD drop hasn't arrived yet, you can refuse delivery (if they ring the doorbell and you're home), then email Q and explain you've refused it and want to cancel its order under the DRS so you'll get your p&p refunded. If you already have it you might talk the into collecting it or sending a pre-paid label but it's difficult to prove that you didn't opt for the AD - it all depends on who picks up the phone in CS when you call I've found. Thanks for the tip, I don't often use Q cut but sometimes an item is available there before it;s live on the website so it's good to know to watch out for this.
The flip side - I find it odd that when I've ordered an auto-delivery item the order details online in my account refer to the single item number which always makes me think I've ordered the wrong option. It also fails to show in your order history if you've opted for easy-pays until you check the confirmation email which is unhelpful!