12d Prison van to stop anticipating shut-eye ...SLAMMER SLUMBER ?? ( number of letters not known yet but possibly 7)
1d Start of operation moving through without separate limits to timing 4 or 5 letters possibly?
13a Single person's ticket's terminal after Greenwich, say 4 or 5 letters ?
H-Hour
is the specific time at which an operation or exercise commences, or is due to commence (this term is used also as a reference for the designation of days/hours before or after the event). (NATO); also known as Zero Hour
I-Day
Bad news is that once originator and theme's location having been resolved some of us are still struggling with the small numbers bit. Life's a *** etc.