He again unsuccessfully sought election in 1857 for Worcester as a Peelite Conservative, and then returned to Stafford to seek re-election as a Liberal in 1859.
[2][7][8] He later returned to Parliament as a Liberal member after a by-election in 1860 — caused by the resignation of John Ayshford Wise — and held the seat until the 1865 general election, when he retired.
[10] He began developing the western border of the estate in 1870, laying out what is now Palmerston Road in around 1870, and building 30 large houses backing onto the New River.
[3][11][12] Upon his death in 1889, the manor and estate were put up for sale, but no purchasers came forward, and it was instead leased to the guardians of the poor of St Mary's Church, Islington; it later became ran down and divided up for development, and then sold for building in 1899.
[3][10] Sidney was also a Justice of the Peace for Middlesex and Westminster and a Deputy Lieutenant for London.