The Three website shows that the Samsung Galaxy S III will be launched for its customers on May 30th and those signing up to the carrier's One plan will get the phone for free. This plan offers 2,000 minutes, unlimited data, 5,000 3 to 3 minutes and 5,000 texts for 34 GBP a month ($54.92 USD). If you text more than make calls, Vodafone's unlimited texting might appeal to you. If you expect to use the browser quite often on the Samsung Galaxy S III, Three's One plan has unlimited data. Picking which carrier to sign up with obviously depends on how you use your phone.
Finally, O2's website is not quite ready. Still, the carrier is taking pre-orders by phone. What we can gather from the site is that the carrier will be offering the Samsung Galaxy S III from free to as much as 299.99 GBP ($484.60 USD) depending on the monthly plan selected.
The international version of the Samsung Galaxy S III has a 4.8 inch HD Super AMOLED display with pixel density of 306ppi. Under the hood is a 1.4GHz quad-core Exynos processor with 1GB of RAM on board. 16GB and 32GB versions are available and the microSD card supports up to 64GB in additional storage. The rear facing 8MP camera has an LED flash, f/2.6 aperture and captures video in 1080p at 30fps. The 1.9MP front-facing camera takes HD video, snaps self-portraits and supports video chat. The device is available in blue or white. While the international model launches at the end of this month, the U.S. version will be rolled out sometime in June.
source: Three, VodafoneUK, O2 via AndroidCentral