The system software update for the PlayStation 4 is now available in the EU and UK online, but you might have a hard time finding it through the terrible PlayStation website search engine, so you can follow the link below to download the update before-hand and miss the inevitable network crash at launch. The full firmware update 1.51 for the PS4 is available here: http://uk.playstation.com/ps4initialise/. You’ll want to download this one if you are swapping out your PS4’s hard drive straight away, as it is the full 859MB system software.
If you just want to update your PS4 and not swap out your hard drive, scroll down to the bottom of the following page, http://uk.playstation.com/home/news/articles/detail/item663044/Update-your-PS4-system-software/, where you should be able to download a ~300MB update.
To run the file, create a folder called PS4, and then in there create another folder called UPDATE, and place the firmware file in there on your USB memory stick.