country seat 
noun British
A large country house and estate belonging to an aristocratic family.Meanwhile, the furious James I revoked Dudley's travel licence in 1607 and, when the renegade failed to return to England, sequestered the estates of Kenilworth, his country seat....
- He was the epitome of the cockney wide boy but what a shock to the system of his new found well-to-do relatives when he inherited a country seat and peerage.
- He was scouting for a country seat for a client who wanted something truly grand, particularly to house his library of 100,000 books.