Did any travellers or people of note every write down why they thought The British were held in high esteem as regard to manners more so than other peoples? So far I have only found this: http://news.bbc.co.uk/1/hi/world/americas/7843154.stm ''A behavioural economist says data suggests Britons in that era were more inclined to be "gentlemanly" while Americans were more "individualist".''
That struck does not say the British were more polite. It says that they were more likely to adhere to a social code about women and children first--at least as it concerned their own female relatives and children.
Politeness is another thing entirely, as is treatment of women and children and men in other area of the world. Indians, Burmese, Chinese, and Africans of that era would not call them polite, as the British were quite oppressive imperialists at that time.