for some unknown reason French people ADD Hs when saying English words starting in a vowel..

Maybe they learnt their English from Cockney speakers, who tend to do the same.
My favourite story illustrating this habit is as follows:

Family party at London Zoo, at the Aviary designed by Lord Snowden. Big argument in progress - "It's a Howl.", declares Grandma. "No it hain't - it's a Heagle," counters young Bert. This exchange is repeated several times, before Grandma spots a Zoo Keeper. "'Ere, young Bill, go an' ask that there man wot this 'ere bird is." Off goes Billy, and comes back a minute later, slightly out of breath, to confound them all with the information. "Hit ain't neither a Howl nor a Heagle - it's an 'awk!"