Actually with it's creation, EASA is becoming a full ICAO member in it's own right, nullifying the individual memberships of it's member states.
It also, in the capacity it been set up by the European Parliament, got every right to insist upon any aircraft based within an EASA member state being registered there - this could hurt.
The quote above only refers to pilots licensing, which is frankly the least of anybody's worries if you are talking about N-reg aircraft (or gliders.....)
Of far greater interest is source of spares, who can maintain the aircraft, approval of modifications and repairs, whether the aircraft has to be on the UK, some EU, or some non-EU register.
G