Sunfish. Not only EN but just about the world over. Best (worst) I had was when flying with German charter operator the F/O replied to a take off clearance with "XYZ Cleared for take off - "bye bye" When asked why he said bye bye, he looked at me with a pitying look (as only local F/O's can do to a foreign contract captain) and said that it was good manners to say goodbye to the tower controller because he would not have time to say bye bye after take off because he had to call departures and say Good morning Sir, this is etc etc.
Unfortunately, the gidday's, cheers, byeeeees, are commonly accepted terminology which have gradually eroded the clipped coldly professional style of radio procedures in Australia characteristic of 20 years ago when superfluous gay chatter was looked upon as amateur ham radio procedure. Which of course, it still is.