The A319s have been mainly removed from Gatwick and several have been sent for scrapping. The Gatwick base will be smaller next summer after the operational difficulties
experienced in summer 2023. 3 A320s from Gatwick are going to Birmingham to establish the base at that airport.
The reduction at Gatwick is partly to improve operational resilience and also due to the returning of leased slots to BA. Already 90 have been returned for summer 2024 with another
140 to be returned over the next year or so. That is the equivalent of about 16 round trips per day. I believe easyjet will introduce more A321s at Gatwick to maintain capacity.
The second hand examples mentioned above are mainly transfers from their European registered company.