However WinSCP seems "confused" about the timestamps of the files. In Windows Explorer we see the same file on both servers with the same time (20:00). We know the files was created at 20:00 and copied to the remote server shortly thereafter. However, when we re-synch WinSCP copies the file back from the remote to the local server with the following explanation:
Remote file '/blah/8834570223646.pdf' [2017-02-27T20:00:00.000Z]  is modified comparing to local file 'D:\blah\8834570223646.pdf' [2017-02-27T19:00:05.948Z] 
The 19:00 UTC is correct but the 20:00 UTC is incorrect (it should be 20:00 CET i.e. UTC+1) so it looks like WinSCP is interpreting the remote server's local timestamp (20:00) as UTC.
When I view the remote server in Filezilla I see 8:00PM (20:00)
Do I need to change WinSCP or my remote IIS FTP to get the timestamps sorted?
option batch abort option confirm off open ftp://user:firstname.lastname@example.org synchronize remote D:\blah /blah # Disconnect close exit