Airbus wing design and manufacture
I would expect the new Airbus wing factory to be in Poland, and the new design centre probably to be in Spain, but maybe France or possibly Germany.
The factory location will depend on local labour costs and incentives to build it in that place.
The design centre location will depend largely on a place the existing UK-based professional engineering workforce would find most attractive: Airbus will want to keep as many as possible of these people.
If I was Airbus, I'd offer the people I wanted a very attractive relocation package, including immediate EU Permanent Residency and 'guaranteed' EU Citizenship in the EU member country of their choice after three years. For the over sixties, a fixed term (4 to 7 years, maybe) agreement with a very large contribution to their superannuation fund as a 'terminal bonus' for running the whole period of the contract
I will be astonished if Airbus wings are still being designed or built in the UK by 2026