Have a word with the ID unit , they will tell you that Easyjet cannot do this because they are required by law to provide a reference.It is not a personal reference just proof that you were there and they can trace your whereabouts for security.
I had a similar experience a couple of years ago when I left GO, the CP did his best to block my move to another airline by refusing to provide a reference for ID purposes. A quick chat with the ID unit and reminding this CP that he would be breaking the law and Hey Presto ID pass issued!