Congratulations on the new job.
The amount and type of work will vary from TOC to TOC but you will almost certainly be deal with the public day to day answering questions, being visible on the platforms, and ensuring the safety of everyone at where your based. You will need to get to grips with your company's timetable, pretty soon you'll be wondering how when questions are fired at you you reel off the answer straight away

Depending on the station you will undertake train dispatch, also again this varies from TOC. All of your roles will be detailed in you contract.
Regarding privilege cards you'll most likely get one card which will allow you to travel across the FCC network for free and possibly other first groups aswell. Youll also get an ATOC card which will entitle you to 75% off of nearly all other TOCs in the country. For london midland your staff card enabled you to travel on london midland, southeastern and southern for free, as all are owned by Govia. Now as a driver at NatEx East anglia I have the same ATOC card, A NatEx East Anglia staff card (free on whole network) and another staff card that enables me to use c2c and East Coast a limited number of times for free.
Hope this was helful!