La Goudale frenchies
You mean TSA drivers, which means they aint necessarily French, when i worked for them there was about a dozen English/UK drivers there
And their yard in St Omer is around 40 minutes off the train/ferry and almost all of it on national roads so they are probably headed for home
Besides if the French gendarme saw a French registered truck running on a sunday they wouldn’t stop them, they’d rather wait and catch any truck from any other country you care to mention and chuck a 1000 euro fine at them instead 
Oh…and one other thing, they have an account at Ashford Truckstop and park/drop trailers in there…thats where i was based when i worked for them
Could have been heading there and then going home to their English houses 