For what it's worth the spreadsheet of Mosquito claims at
http://www.mossie.org/Mosquito.html gives the Werk Nummer of U5+AA as 260391 but I am unclear as to the source or why it differs from the information in ULTRA. Given that the aircraft was shot down over the Channel, the matter is unlikely to resolved any time soon but it clearly isn't the machine which came down near Havering.