superflanker
You might find the following links useful. The
first one will download: NOTICE TO STAKEHOLDERS: WITHDRAWAL OF THE UNITED KINGDOM AND EU RULES IN THE FIELD OF REGULATED PROFESSIONS AND THE RECOGNITION OF PROFESSIONAL QUALIFICATIONS. The
second one will list the professions in question (airline pilot included).
I'd recommend that you get your licence before 29 March 2019 and then transfer it to that of another EU nation (Spain/Ireland?).
Needless to say, this situation and many other similar ones would not apply if the UK "government" opted to remain in EEA as an EFTA member.