Monarch are my airline of choice from BHX ,although on my one flight to date on Jet2 I was mighty impressed with new aircraft and sparkling ground and cabin staff.
Having a premium leg room cabin appeals to pax who prefer paying £15 for these rather than the same for wing exit seats on FR and find the trolley has run out of f&b when it gets to you! And the 23k luggage is the best in class.
I have never found Monarch attracts the vest/tattoo/piercing groups that other LCC experience and they are seldom in the press for pax problems.
That is why to many "more mature travellers"it is their airline of choice.
A poll of 10 pals at the gym,average age 55, 80% use Monarch as their first choice unless the flight times are cr&p then they use Jet2 or Ryanair/FlybeVueling)