TheFork users who ate in Lambersart have said really good things about Il Ristorante Lille, Les Hauts de Lille - Hôtel Barrière Lille and La Connivence. Maybe you should give them a try!
Some of the more popular Escargots restaurants having a terrace in Lambersart according to TheFork users include:
Le Bistrot Lillois, with a 8.8 rating
Estaminet Au Soyeux, with a 8.7 rating
Goudale, with a 8.4 rating