L&M Companion says..
A village on the Middlesex bank of the Thames, 2 miles upstream from London. A stretch of marshland effectively divided it from Westminster, but its proximity and ease of access by road and river ensured that it was well tenanted. Its gardens and reputation for good air added to its popularity. According to one estimate, it had under 40 houses in 1664, but the hearth tax of that year shows 12 with another 36 too small to be taxed.
Little Chelsea was a hamlet upstream from the main village and in the parish of Kensington.
What a difference nowadays...Kensington & Chelsea is the most expensive borough in London with an average house price of £636,914.