John Finch, rector of Winwick and brother of the Earl of Nottingham, gave him access to his collection of paintings so that he could study and copy them.
Finch arranged for him to study in London at the Kneller Academy of Painting and Drawing founded in 1711 in Great Queen Street, Lincoln's Inn Fields.
After returning to London, Winstanley continued to act as an agent for Lord Derby, bidding and buying on his behalf from auction houses and art dealers.
The Yale Centre for British Art holds a sketchbook containing 81 study drawings of body parts by Hamlet Winstanley.
His etchings after pictures by old masters (including Ribera, Rembrandt, Anthony van Dyck, Carlo Dolci, Tintoretto, Titian, Rubens, Frans Snyders, and Salvator Rosa) in the possession of the Earl of Derby were bound together in a portfolio known as the Knowsley Gallery.
Winstanley executed portraits of the Stanleys, John Blackburne of Orford Hall, Samuel Peploe, and Jonathan Patten of Manchester.