The calculated distance (air line) between Saint-Leu-la-Forêt and Lille is approximately 117 miles respectively 189 kilometers.
By car or train, the actual journey to Lille is certainly longer, as only the direct route (as the crow flies) between Saint-Leu-la-Forêt and Lille has been calculated here.
Air line (approximately)
189 kilometers
102 nautical miles