There won't be regular ops on the 737 out of birmingham for some time. No cabin crew there is trained on it. Just 757/767 so the 1 or 2 weekly 737 flights(if they even have them this year!!) will be done as a W pattern out of another 737 base such as DSA/EMA/MAN etc...
E.g.
(EMA-AGP-BHX-AGP-EMA)
only way to tell is if you leave before you arrived the previous week or you leave after double the flight time the previous week.