As a rule Monarch do not recruit directly on to the A300. The A300 operates the whole range of flights that Monarch offers, with the vast majority being charter. Ie 1hr ski flights (LYS or TLS), short hauls eg (AGP,ALC,PMI) medium short eg (TFS, BJL, SSH, TBA) all the way upto long hauls flights like GOI. Although these flights will tech stop in BAH. (BAH being like a second home to A300 crew in winter). Much ad-hoc work is also undertaken on the a300.
With 320,321,330 fleets, crews are not selected directly for a330. That said, pilots are rated on both 320 and 321 with a330 rated pilots, rated on all 3 types. The A330 operates 90% long haul and most notably (various Caribbean destinations, Cuba, SFB and YYC) and eastwards such as GOI, MLE and CMB. A330 selection is primarily done by seniorority, with many already waiting for their turn, so don't go holding your breath for quick selection.
The 320,321 operate probably 75%+ of the scheduled service flights. These range from the significant number of flights to southern Spain, Gibraltar, the Balearics to longer canaries sectors. Little seasonal variety between schedule or destination.
The 757 workhorse operates probably an equal mix of charter and scheduled flights. There are also some long haul flights operated (BAH, TRV). In addition, the versatility of the aircraft makes it very acceptable to the ad-hoc market