Don't resign! Stay on and insist on a compromise agreement. You'll still end up with no job as if you'd resigned, but you will have the terms of everything, including your reference, in writing, and possibly a cheque. It sounds a little like they are trying to get you to resign without a compromise agreement, which leaves you open to them changing things in the future, including giving you an awful reference or refusing one completely. Also, if something has to go to the GTC, it will, whether you resign or not.