Anthony Carn, these are 2 different scenarios and as I understand it is covered by 2 different things in the UK. The hypothetical case you say is covered by TUPE which is a transfer of undertakings to protect employees, you would need to talk to someone more knowlegeable about it than me, hopefully this will help some what.
What helitubbie comes under redundancy and is regulated by the dti try
here
You may have to involve lawyers/unions, for redundancies I know that depending on how many are involved determines how much notice a company has to give,
thirty days before the first of the dismissals takes effect in a case where between twenty and ninety-nine redundancy dismissals are proposed at one establishment within a ninety day period;
ninety days before the first of the dismissals takes effect in a case where one hundred or more redundancy dismissals are proposed at one establishment within a ninety day period.
hope that helps