There is a very long tradition of mispronouncing French words in UK - as the Saxons just couldn't get it right! So much so that many English words are now imbedded in the English language and barely resemble the original lol. Like 'beef' for 'boeuf', or 'plumber' for 'plombier' or even 'mushroom' for 'mousseron', and so many more. 'Cul-de-sac as kept the original spelling, but any French would find it difficult to recognise the English version.
My French students always laugh at the word 'genrE', or 'ménage à trois'. One mistake that does grate (a bit) is the common mixup between 'ménage' (a household/family) and manège (for horses, or a merry go round).
And it goes both ways - I always have to explain to my French and Swiss students that a 'sweatshirt' just cannot be a 'sweet' (which is how the French say it) for obvious reasons.
All good fun and confusion.