The device can be yours for free if you sign a two-year contract that's at least £34 per month. That cheapest option nets you 500 minutes, 5,000 texts, and 1 GB of data each month. For £3 more you can get unlimited data, or you could choose Three's The One Plan. That costs £40 per month, but brings you 5,000 Three-to-Three minutes, 2,000 nationwide minutes, 5,000 texts, and unlimited data.
Or if you'd rather not do any contract signing, then you can get the Sensation XL on Pay as you go for £449.99. It's your choice really. Whatever that turns out to be, head over to Three to place your order.
And before you compare the Sensation XL to the Samsung Galaxy Nexus, do remember that the latter doesn't have any touch-sensitive keys below the screen, which, alongside the display's different aspect ratio, makes it narrower than the Sensation XL (though not by much).