Wouldn't recommend making up a reference, BAA will withdraw your ID if they happen to find out. The Regulation states that if an ex-employer refuses to give a reference, he must write a letter to your new company stating that they refuse to send a reference, and it must be in the company's letter head standards. You will then need to ask a friend to vouch for you that you were employed during the dates you mentioned by that company. Hope this helps !
All the best...
PS. And don't worry, you won't get the bullet because of references issues, it's not in your new company's interest to fire you after investing in your training
