Beaware that the basic NATS GPS unit doesn't have most of the featues that are standard on GPS systems. Eg, it has no route planning, no nearest functions for an emergency diversion, no breadcrumbs, and has no info about any airport other than what's shown on the paper chart. These are some of the most useful features of a GPS.
All the NATS unit will do is tell you where you are, and warn that you are about to enter controlled airspace.
There is an add on (costing almost the same price again if I remember correctly) that will add some of these features, but that makes it more expensive than many other systems.
dp