Last time I was there was in February. Landing and handling came to 14 Euros. I didn't stay very long, so no parking charges, but I doubt they're hugely expensive. Make sure you let them know you're flying as a member of a flying club, not a private owner, otherwise the charges are a lot higher.
Lille's a large airport but quite welcoming of GA - albeit there isn't much of it, so they have to send someone from the main terminal especially to take your landing fee.
No need to give customs/immigration any notice, which makes life easier.