Hi there,
Just going to give my two cents here (or pence), you don't have to be over 18 to get an airside pass!! As long as you can give 5 years of employment or education then your sorted!! We have a number of under 18's working for us, well they where under 18 but all growing up now. I was 17 when I started at LHR and have worked my way up now been there 9 years and am now in Operations and Dispatch. I wish you luck in your hunt for a job at BHX, nice little airport to work at and also welcome to the mad bad world of ground handling!!