I grow weary of people taking the piss out of David Prowse’s on set delivery. He was wearing a mask so he had to yell for the other actors to catch their cues. He knew the voice would be recorded in post production but was led to believe he would be doing it. He was an actor. If given the task he wouldn’t have performed it in his own Bristol accent. Would it be as good as JEJ, doubtful, but it wouldn’t have been the same voice he used on set. Anthony Daniels also knew his lines would be rerecorded so he too used his natural voice. Lucas intended Threepio to sound like a used car salesman but when he heard Daniels on set voice he called him back to exaggerate that performance and Threepio became a fussy butler instead. Despite the crappy way Lucas treated Prowse (and the other Darth, Peter Serafinowicz) Prowse and JEJ both praised eachother and he did a lot of charity work before his death. But yeah it would be funny. Artoo was originally going to speak English too.