You have to be on the job for a year before you can apply for your FIP card and any European coupons.
You get 1 or 2 coupons per calendar year on most of the European operators, with each coupon valid for up to 8 days (2 per "box") in 3 months from the date of issue, though they cease to be valid once you return to the UK.
As regards to applications for International Travel Facilities, Rail Staff Travel recommend applying 4 to 6 weeks in advance to be on the safe side, though FIP rules say that boxes should only be issued within 2 weeks of travel.
Download the "TOC New Entrants" guide from the
ATOC website and it'll tell you what you can get, including Heritage Railways in the UK.
All the necessary forms for Staff Travel facilities can be found
here and in most cases you can send them directly to Rail Staff Travel.
HTH,
Barry