The key point being that BA will have suspended LGW short haul til they have a view on the likely market next summer. The fleet is already down by 28 B744s and 12 A380s with no flying undertaken by the A321CEO fleet whatsoever. Given Winter is likely to be a bloodbath, I am not convinced they'll be back next summer. If LHR reinstates the 80/20 slot usage role for the summer then as much of BA's London program as possible will be at LHR protecting slots. Given BA will be 20-30% smaller going forward, they really do need to protect market share at home base as the likes of Westjet and others grab the slots that come up. If BA did not use 10% of their existing LHR slots, Wizz and easyJet would bid for them IMHO.
Hence LGW becomes a side issue and LGW slots are almost worthless in the current market. I expect the whole G-GAT* A320 fleet to exit formally soon.