Ian,
The one that always gets you is an afternoon standby say 14 to 2300. You wake up at 0800 as your body clock says wake up. And off you go to do things for the wife/kids etc then at 1430 ring ring "we need you for a flt" " 1630 report A/Line to say Glasgow hang around for say 4 hours then operate.
say GLA - AGP(Malaga) - LTN (Luton) throw in a little delay and discretion and whoa! you are landing at LTN in maybe bad weather having been up for something like 22 hrs. All quite legal. (Note hav'nt got my CAP371 on me at mom but the above gives you an idea of what
actually happens for real. Substitute any flt from GLA that works to the FTL and it works out virtually the same)