To clarify why (I think) there won't be a cliff-edge for aviation...
1. EASA AML Cancellations: As you all say, there's too many of us GB mob all about the EU to do without, suddenly.
2. Forms 1 becoming invalid:
far too expensive for all airlines to suffer re-cert costs...
Airbus will suffer wing production costs
RR costs will also go up
Dowty, etc, etc.
3. Closure of airports to UK traffic: All North Atlantic routes for the EU are controlled by UK ATC..!
4. Most part 21 design orgs are in the UK for interiors, repairs, mods etc....
5. too many EASA employees are UK based persons...
I have confidence, however seemingly misplaced, that a fudge will be found...we can only wait and see.