I’ve just found out that apparently ‘to sleep for England’ means ‘to sleep for a very long time’. How popular is this saying? Here is the passage of the book ‘Snap’ by Belinda Bauer:
His head nodded on to his chest. He was so tired. He could sleep for England.
This expression is quite common used in a lighthearted manner. The idea comes from what is normally a description of someone competing in a sport for their country. In other words you reach a ‘professional’ level in sleeping. You could equally say - He could sneeze/snore/shout for Britain - doing something to excess.
Hi Alan, maybe we should modify the expression to ‘do something for Brexit’ 
What an excellent idea - I like it - Sleep for Brexit !!!