Mode S: I don't know what exactly is written in your stuff you get from NATS, but the Modem S is definitely a typo.
Mode S information is only available at certain units at the moment - although a lot of information is obtained by the aircraft, you can choose to only display a set amount of it (TC often display the level that is set, heading and IAS in addition to the 'normal' data displayed in the data block - e.g callsign and level). I'm pretty sure there's a way of getting more information if you want it, but at this time, it's not necessary and you wouldn't want to be wasting your time looking at it when you should be controlling the traffic!
Does that help?