The KitKat chocolate bar as we know it was invented in Britain in 1935, and now British owners of unlocked S4 and Note 3 devices can enjoy the chocolatey, wafer-y goodness of Google's very latest software, Android 4.4.2.
Owners of the S4 flagship phone and Note 3 phablet are reporting the 4.4 update is available to download over-the-air. If you can't see the update yet, it could be because it hasn't yet been pushed through your network. Your phone should inform you when you're ready to update, or you could try to update manually through Samsung's Kies software on your computer.
KitKat isn't a huge change, although you will notice some icons have changed colour. The phone dialler has a new, simpler design, while your contacts are organised based on who you speak to the most. The Hangouts app now combines your hangout conversations, text and MMS messages in one conversation thread. And you can say "Okay Google" to activate voice control and speak to search or dictate text messages.
Probably the most useful improvement is that KitKat uses less memory, affording smoother multitasking and longer battery life.