iPhone 4S goes on sale

3 iPhone 4s

Apple's updated iPhone 4S smartphone goes on sale today in the UK.

Apple, and the mobile operators, have been taking pre-orders since last week. The phone has already sold out on the US networks AT&T and Verizon; worldwide pre-orders are reported to have reached the three million mark.

Here, Apple has opened some of its retail stores early to cope with demand. However, the company has run into difficulties with its iCloud and iOS 5 update, with users complaining of problems downloading the software. The new iPhone comes with iOS 5.

If you are considering an iPhone 4S, check out our iPhone 4S: need to know and iPhone 4S: first impressions articles. Owners of earlier iPhones, and of iPads, can also find out the essentials on the new OS in IT Pro's iOS 5: need to know round up.