Interesting question. This is something that came up extensively in my research of the Westons of Cranbrook and Tenterden and related families in Kent during the 18th century, so I thought I'd take take a more detailed look at it this morning. I'm not sure how far these practices are influenced by geography, chronology or status, so I've tried to include information on all three.
The furthest back that I can trace my paternal line is to farmers in Mayfield in East Sussex from about 1425. They used Weston as a surname, did not use middle names and had very standard first names, usually William, Thomas and John. When the parish registers at Mayfield commenced in 1570, different individuals in the parish who shared the same forename and surname were differentiated by giving a parent's forename, an indication of age, or the location where they were living. Sometimes a combination of all three was used e.g. "little John Weston the sonne of John Weston of Sharndean". Some 9% of the parish registry entries are concerned with the many Weston families in the neighbourhood! The most propertied of them use the term "yeoman" to describe themselves.
The first unusual forename is Mersham Weston in 1602. Mersham is the name of a village in East Kent, a surprising 30 miles from Mayfield,
In the mid-seventeenth century, one branch of the family had moved the much shorter distance to the booming woollen broadcloth producing town of Cranbrook, in west Kent. Heads of the family started to call themselves "clotheir" from 1668, then, gradually, from 1698 onward "gentleman".
In 1750, a third son was given his grandmother's maiden name of "Stringer" as a forename. Without any further intermarriage with the Stringer family, Stringer became an occasional family name, being last deployed in 1896.
The first use of a middle name was in 1770 when Elizabeth Hyland Weston was given the maiden name of her maternal grandmother's mother. At the end of the eighteenth century, her branch of the family moved to Tenterden, becoming gentleman sheep farmers and civic leaders (eleven times mayors or the town). Of Elizabeth's seventeen nieces and nephews with the Weston surname, nine had middle names and only two of those were not the surname of a related family.
Thereafter, maiden names got perpetuated as middle names within the family. The frequency of use may have corresponded to the importance of the connected family. Most tellingly, in 1784 John Tempest Weston was given his maternal grandmother's maiden name. The Tempests are one of England's very ancient aristocratic families and the Westons carry on celebrating the connection by occasionally using that name right up to the current day. Sometimes the use of the name is according to a formula: in my own branch of the family, the eldest boy in each generation since 1810 has had a middle name of Pix. Sometimes the name is used for all the children. I don't have an example of a "double barrelled" surname (nowadays so customary) using the name Weston, but Catherine Weston married a Charles Henry Rogers Harrison in 1845, and some of their children began to hyphenate his last two names as an indivisible unit from then on.