Combe Magna is the residence of Mr.Willoughby which is said to have an income of £700 annually. It is described as about 30 miles away from Cleveland, the residence of the Palmers. When Willougby is disinherited by his aunt, Mrs.Smith, he seeks out a rich wife so that he can obtain the funds to maintain his lifestyle. He ends up marrying Sophia Grey who has an inheritance of £50,000. Consequently, they spend their honeymoon at Combe Magna, which is also where he's staying when he comes to call on Elinor and Marianne during the latter's illness, and comes to call and try to explain his previous behavior. 

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