Why would companies do this though? Surely they'll try and get away with paying the bare minimum?
Well it was voluntary redundancy, so they sent out offers to everyone and a certain amount of people said they'd like to take it, then they picked who they were going to let go out of the people who volunteered. These people also had 6 months between their leave date and finding out they were leaving. It's pretty bad for morale at a company when they make a load of people redundant, even the people who don't get made redundant will start looking for new jobs as it looks like they're on a sinking ship.