I know Monarch, British Airways, Easyjet all mostly used Airbus A320-200 At GIB.
Titan Airways have 3 x A320-200 (168-180 seats) and are due to reconfigured the leased Airbus A318-100 to 112 economy seats in the first quarter of 2018. I think Gib government & local businesses are part funding this and assume if they are they will be wanting A320-200s if possible.