Likely a pricing error
[Update: The page has since been pulled. Sorry to anyone who was too late.]
GO! GO! GO! Right now on PSN in the UK the Fallout 4 Season Pass is available for free.
Yes, this is most likely a pricing error. Yes, there’s a fair chance you may not get to keep it. Still, if you want to give it a shot, it’s free right now.
So, let us know if it works for you.