12000 cases is 144000 bottles assuming 12 per case and the definition of case seems to vary between 6 and12!

British Airways - BRITISH AIRWAYS FACTSHEET

They carry 123,000 passengers per day. Say 1% are first. 1230 people.

Say they drink half half a bottle each. Some 600 bottles a day.

The stash would last 240 day and Concorde retired long long ago. Whatever way you fudge my simple maths if they were using it at all I suspect it is long long gone!