Akerosid - the issue *probably* falls under the Maastricht 'second pillar' and therefore requires unanimity. You can bet that the German Presidency, which wants to have this deal signed on their watch, will be working hard to bring the Brits in line.
As for cabotage/5th freedom opportunities - there was a time when Europe was crisscrossed with US 5th, Pan Am then Delta had a huge Frankfurt hub operation, TWA, Pan Am and subsequently United had a number of key routes out of LHR. TWA had a sizable part of the Rome-Athens market. All gone.
The only US 5th in Europe nowadays is express parcels.
Barit1 - 'BA would love to operate a LAS-JFK segment' - you must be joking.