I'm a native English speaker but I've been reading some Discworld books in French partly to brush up on my rusty A-level knowledge of the language.
I'm currently reading Men at Arms / Le Guet des Orfèvres and it's interesting to see how some of the less correct English used by eg Gaspode is translated. For instance, 'dunno' is 'chaispas' (a contraction of 'je ne sais pas'/'I don't know') 'wossname' becomes 'chaispasquoi' ('I don't know what').
Various contractions are used to give Gaspode what I'm guessing is the French equivalent of a sort of rough East End of London way of speaking: 'T'as d'la veine que j'sois là' for instance, instead of 'Tu as de la veine que je sois là' ('you're lucky I'm here'), and the 'ne' is missed out of negative phrases: 'j'suis pas membre' instead of 'je ne suis pas membre' ('I'm not a member').
Also it's interesting to see who uses 'tu' (the informal 'you') and who uses 'vous' (the formal 'you'). Carrot and Angua, for instance, use 'vous' to each other throughout, even though I'd have thought Carrot would say 'tu' to Angua as he outranks her. Angua and Gaspode use the informal 'tu' to each other straight away, and Nobby and Colon are also on informal terms. Death, as a consummate professional, uses 'vous' to all his clients! Does this stay the same in other languages where there's a similar distinction?
(PS - Apologies for any incorrect French)