Simon 150; Carls official title is GMFO (General manager flight ops)
As for some of the other questions i'll try.
I haven't got any pay scales in front of me so can't answer the salary question.
As for work life you should get a minimum of 9 days off a month.
On average you will be away about 10 nights a month, this varies quite a lot and some months it will be higher and others lower. You can request 'max touring' but this doesn't always work!
Summer and winter are equally busy.
There is no average amount of stbys per month, you might get 2 or 3 one month and none the next.
You need to be at the airport within 1 hr from call out on a stby. (Although this may have changed recently I can't remember!)
I have no idea about the need for a National insurance number, we already have people from other parts of europe working for us so it is definitely not a way of only employing British nationals.