"First in, last out" no longer applies in law in the UK and hasn't done for a number of years, regardless of what is in your contract.
In the eyes of the law, your contract of employment automatically changes when new legislation is passed which pertains to the terms and conditions within your contract, your HR department should tell you of these changes.
Providing that employment law (regarding age discrimination) is followed to the letter, it is perfectly legal for a company to make more senior staff redundant over younger (cheaper to employ) staff.
Not much help to you I'm afraid, but BALPA don't seem to do a huge amount for their members unless publicity is involved, if I were you I'd seek help from a "No win, No fee" lawyer.