Originally Posted by
sydunipete
Eurostar really is a great service and avoids all that messing about getting to LHR or LGW (depending upon where you are staying) and ditto for the other end. Trains really do go to the heart of a city. By the time you went from St Pancras to LHR, checked in, waited, security etc etc you'd probably already be in Paris on the Eurostar (2 1/2 hours).
...........
From Lille or Brussels it's not hard to reach the Word War 1 sites of Belgium and Northern France. They are incredibly moving.
I think I'd keep it simple and head to Paris and focus on just a few neighbourhoods.
If you go to Lille and are a foodie , or even if you're not, try and get a reservation for
Rouge Barre 50 Rue de la Halle 59000, Lille https://www.rougebarre.fr/ Small place with excellent food. I think the owner won MasterChef France or came in second or something. Anyway it's small and you need a reservation usually even for lunch. It's in a quiet neighborhood. We thought we were in the wrong place because it's certainly not a commercial/touristy part of town,