Hi,
Ok, let's go with Wednesday the 17th November.
Sunset on the 17th is at 16:08, so shall we meet at 3:00PM at Victoria Train station?
Exit via the Victoria street exit and wait on the pavement shown here:

A few potential places of interest, with walking times from Victoria station.
Tate Britain 18 minutes
Westminster Cathedral 5 minutes
St James Park station/Broadway 10 minutes
Birdcage Walk 14 minutes
This may help plan photos for the 'blue hour'.
See you on the 17th.