Selection for dismissal by reason of redundancy must be fair; one commonly accepted selection standard which passes the standard of fairness is 'last in first out' but it is important to remember that this is by no means the only fair way to select people for redundancy.
So - worst case scenario: existing management team can be dismissed by reason of redundancy with statutory redundancy only.
In this scenario, it would have to be demonstrated that this is a fair process. For example, the new owner could not easily get away with dismissing existing management and then simply hiring new people off the street; but if they have their own management team ready to move in, it might well be reasonable to say 'as part of the re-organisation, we are putting in place our own experienced managers, any existing managers who can not be re-deployed will be redundant'