Someone highlighted this a couple of months ago and many of us missed the offer. I just went and picked two items on the Amazon site and I was offered the "Amazon Prime" free trial. For 30 days, I can order whatever I want and get next day delivery. After that, I can have the service for £49.99 a year. Of course you can cancel prior to the 30 day period, so there's no real committment until the end of the trial!
Grab it while you can - great offer!