Which house did Pitt rent on Park Place?

After Pitt's resignation in early 1801 he needed a place to live. His mounting debts could no longer be ignored, and although he did not sell his country villa at Holwood in Keston, Kent until the summer of 1802, Pitt needed somewhere to rent in central London. Therefore, in March 1801 a small furnished terrace house on Park Place in St. James was found. Pitt took over the rest of a one-year lease of the property when its former tenant, Edward Fisher, a retiring Under Secretary at the Foreign Office, left London for Lisbon.

Park Place became Pitt's main base in London until about the middle of 1802 when he moved to another rented accommodation on 14 York Place (now part of Baker Street). What baffles me - and it has done so for several years now - is which property on Park Place was actually occupied by Pitt? Earl Stanhope, one of Pitt's biographers of the early 1860s, claimed in his notes that Pitt lived at number 5 Park Place (see the Stanhope of Chevening manuscripts, Pitt Mss at the Kent History & Library Centre in Maidstone, Kent - U1590/S5/C60-C64 for more information). In contrast to Stanhope, Pitt's well-known 20th century biographer John Ehrman states, in a footnote on pg. 534 of The Younger Pitt: The Consuming Struggle, that the house on Park Place was said to have been number 12. A direct source isn't quoted for this information. 

So who is correct - Stanhope or Ehrman? In either case, the properties (be it no. 5 or no. 12) are no longer in existence. On viewing my digital copy of Horwood's 1799 map of Park Place, St. James, no. 5 and no. 12 are on opposite sides - and ends - of the street. Where number 5 was located in 1799 is now a modern late-20th century block of flats, and number 12 is (I believe) now an early 20th century terraced house.

What's fascinating to me is how these two biographers managed to come to such a different conclusion on the property number of Park Place. Yes, Pitt only lived there for a single year, but it was a place connected with him at an important juncture of his life - the time of his ministerial resignation. If anyone knows any information about this I'd be happy to hear from you!