English people were perceived by XIXth century French as eating copious amounts of meat (in particular beef). As an example, when the famous French romantic memorialist Châteaubriand mentions his stay in England as an émigré during the French Revolution (Livres VI, VII and VIII of the "Mémoires d'Outre Tombe"), he regularly discusses "roastbeef" or "copious amounts of beef" :

"L’homme aux ressources, Peltier, me déterra, ou plutôt me dénicha dans mon aire. Il m’emmena de force, avec La Boüétardais apoplectique, et deux émigrés en guenilles qui se trouvèrent sous sa main, dîner à London-Tavern. Il nous fit boire du vin de Porto, manger du roastbeef et du plumpudding à en crever." (Livre VIII, éd.Garnier, 1910 (Tome 2, p. 107-176))

"The man with resources, Peltier, unearthed me, or rather, picked me up from my burrow. He forced me to dine with him at the London Tavern, along with an apoplectic La Boüétardais and two other émigrés that he came upon. He had us drink Port, and eat to the death roastbeef, and plumpudding"

Another passage ;

"Un dîner d’énormes poissons et de monstrueux quartiers de bœuf restaure monsieur l’ambassadeur, qui n’a point d’appétit et qui n’était pas du tout fatigué." (Livre VIII, Garnier, 1910 (Tome 1, p. 315-439))

"A dinner of huge fishes and monstrous slabs of beef fills up M. Ambassador, who had little appetite and was not tired at all"

This association, of British customs and generous consumption of beef, is also found in the periodical publications of the period : in the Revue des Deux Mondes (L’Angleterre et la Vie anglaise. — VIII. — Les Clubs de Londres 2e période, tome 26, 1860 (p. 769-820)), which is typically the kind of journal that Verne would have read, we can read : "C’était un vrai dîner anglais, où l’on célébrait le bœuf et la liberté, auquel se mêlaient les gais propos de table, et qu’assaisonnaient les appétits britanniques." ("That was a true english supper, where beef and liberty were celebrated, in unison with jolly table talk, and peppered by British appetite").

French people of the time were in particular impressed by the British custom to cook steaks on an open fire or directly in a greased pan, rather than stew beef (which was the typical way of consumer beef in France at the time, like in the Boeuf Bourguignon for example). The French words 'rosbif' (beef fillet) and 'biftèque' (beefsteak) are direct translitterations from the english, when these methods of cooking beef (which require logistical progress and availability of sufficiently fresh meat) were imported to France in the XIXth century.

Ironically enough, right now, the "Steak Frites" is considered a basic staple of French food (see Mythologies by R. Barthes for example, where it is considered a "myth" of the French culture, in the barthesian sense), while it didn't originate here ; as a French man, I'm obligated to mention that conversely, you'd have a hard time finding decent food in the UK.