To the left is a detail of a map of London produced by John Rocque in 1746. This detail is centred on Whitehall and shows Charles Street running between Duke Street and Parliament Street. Charles Street is now named King Charles Street. It has been extensively redeveloped and the site is now occupied by a number of government buildings.
The area has changed dramatically in the last 250 years. Most of the Houses of Parliament were rebuilt after the disastrous fire of 1834 while the Thames was embanked in 1864-1870. The sites of London's main institutions have not changed, however, and it can be seen that Sancho's shop was sandwiched directly in between two centres of power: the Prime Minister's house in Downing Street and the Houses of Parliament, both just a few minutes walk away. Today, even more centres of power sandwich King Charles Street which has the Treasury on one side and the Foreign Office on the other.
Many other famous landmarks are close by. To the north lies Charing Cross, now the site of Trafalgar Square but then the location of the pillory, while to the immediate west is St James's Park and the palace: the focus of fashionable life in the mid century. Westminster Abbey is close by and, in Sancho's time, the new Westminster Bridge, completed in 1750, connected the north and south banks of the Thames.
You can compare the old map by looking at this Modern Map of Westminster. It is interesting to note that while many buildings have changed, the underlying street plan is much as it was in Sanchoís time. Indeed, the main thoroughfares remain now much as they have been since the Middle Ages.