Combe Magna is the estate of Willoughby that resides in Somerset. Following his disinheritance from his aunt, Mrs.Smith, that remains his only source of income. Unhappy with his economic state, he marries a woman, Miss Grey who has a fortune of £50,000. Combe Magna is said to be about 30 miles from Cleveland, the estate of Mr. and Mrs.Palmer (nee Jennings). When Marianne falls ill at Cleveland, Willoughby, who had been staying there, comes to visit and explain himself to Elinor. During their conversation, he tells her that he and the new Mrs.Willoughby (nee Grey) spent their honeymoon at Combe Magna. 

Austen, Jane, and Kathleen Viola James-Cavan. Sense and Sensibility. Broadview Press, 2001.