TR,
Not a sub-contractee? You're sure?
Who's your contract with? Who's your union, Balpa BACC or BACX? Where do you get your seniority from? Which piece of paper would you refer to if things went wrong for you, your BA contract? Where do you get the right to bid from, Ba or BACX? Have you signed a contract with BACX?
Trust me, it doesn't matter what the cosy arrangement appears like to you, in my experience a forensic analysis by the employment tribunal will determine who your employer really is. Quite often, the intention of the parties fails to reflect the actual contractual position of the parties.
So, if for one moment the tribunal thought you were employed by BA but 'sub-contracted' to BACX, then they'd expect your sorry arse to be fired before any employee of BACX.
You've got to decide which cake you want to eat, cos the tribunal ain't gonna let you pig out on both.
'round midnight