@Anonymous User
Welcome to the forum.
You don't necessarily need a NOW TV box, but if you don't have any other suitable device you will probably find the NOW TV box the cheapest option. You can buy various combinations of a box on its own or with bundles of passes here
http://www.nowtv.com/box
or at places like Argos, Game, Currys, Tesco etc.
However have a look first at this list of compatible devices. Certain models of LG smart TVs have the app, and you can get it for Xbox, PlayStation etc so you might already have a suitable device you can use
http://help.nowtv.com/article/Supported-devices
The following help page explains how to get the app on different devices
http://help.nowtv.com/article/How-to-Get-NOW-TV-on-your-device
