Back when I applied to NATS (10 years ago...) there was pretty good description of the north Atlantic track system in the literature sent out to applicants, and many of the questions were a test of whether you'd done the reading - there was a reading list given too and it wasn't long!
INS uses gyroscopes which measure accelerations in all directions to constinuously update the position of the aircraft. It is so accurate that it is set up using the lat and long of the individual stand at the departure airport.
You might want to mention RVSM (reduced vertical separation minima) which allows suitably equiped aircraft to use 1000 ft vertical separation above FL290 rather than the 2000 ft used between non-RVSM certified aircraft and in non-RVSM airspace. The Shanwick FIR is RVSM airspace. If you get that in, they'll probably assume you've read enough to show willing. Ultimately, that's what the interview is all about. If you knew it all already, you wouldn't need training! They want to know that you're dedicated enough to the job to do some research. Good luck.