I was just reading the Making of Star Wars and Lucas talks about how the HO wouldn't allow Harrison Ford, Luke (what's his name?) and Carrie Fisher into the UK to work (old rules - don't even know them). His lawyer called them up and said that if they didn't have Visa's down to the studio by the next day he was pulling the project. He said officials were waiting at the gates the next morning.
He goes on to talk about the differences in British v. American work attitudes, not really disparaging the Brits, but he couldn't get over that at 4 o'clock everybody just dropped their stuff, no matter what was happening, and meandered off for tea and biscuits.