Currymonster - don't fret about calling Warton. They are (without exception, in my experience) friendly and helpful. Just ask for FIS and MATZ penetration, they'll give you a sqawk, and after that they'll only contact you if there is traffic you may want to know about. On my first solo nav I was unsure of position (oh alright, a bit lost) and they went out of their way to get me to a position where I was happy to get home from.