TheFork users who ate in Le Bec-Hellouin have said really good things about L'Archange, Le Petit Coq aux Champs and Le Petit Pont. Maybe you should give them a try!
Some of the more popular European restaurants having a terrace in Le Bec-Hellouin according to TheFork users include:
L'Archange, with a 8.4 rating
Le Petit Coq aux Champs, with a 9.1 rating
Belle Isle sur Risle, with a 8.6 rating