Thanks Stevelup - that link is most helpful.
It does highlight my initial confusion.
If you look at the link that Stevelup supplies and look overhead Calais for example - the main map suggests that the frequency to call is Paris Ctl on 128.275. But in the smaller 'Flight Information Frequencies' map at the top right it suggests that Lille Info (listed as number 10 with three frequencies listed) is the right unit.
From what you've all said it sounds like you could call either and they would look after you but keen to know what the difference is.