Has anyone been in a tupe?

I work in a small firm that is in process of selling to a large firm. We have been told to expect the same contract terms or better because we are being tupeed?

Has anyone gone through this before and what is involved? Does the employee have a right to not accept? Or negotiate terms individually?

If some members of staff have been employed for less than 2 years then I guess they would have less security during this process?

Some context: been employed over 2 years. Have been considering moving employers or starting self-employed and want to know where I stand in this process.