yesterday after discussing this, I asked multiple people I know from across the country, including the midlands, and they all said that no, cheers is not something they've ever heard as goodbye. I stand by the fact that cheers means thank you/regards, and occasionally is used in place of or alongside goodbye when some kind of transactional behaviour has taken place
you're misunderstanding the nuance of it. when other people are leaving the office and they say cheers, they're saying a short form of "cheers for working with me today" more equivalent to "regards" than "goodbye"