The Sandwich Man - location

I notice that you have the wonderful old 1966 film The Sandwich Man listed on your site at www.reelstreets.com/londonr-z.htm
A lot of the scenery from the film will be very familiar to most people who know London - Upper Regent Street near the monument, Trafalgar Square, Pall Mall and so on - but there's one particular scene that has always troubled me since I first saw the film a few years ago. I lived in London for seven years, but I have no idea where it is - it's the public toilet where the drunken city gent mistakenly goes into the ladies - pic here:
homepage.ntlworld.com/jgibbon/images/where1.jpg

I would gladly provide the required tenner if one of your readers could identify the location!
Best wishes, James

Well James
You owe ME the tenner............just by Coram Fields, is it Brunswick Square or Grenville Street WC1
How was that for instant recognition

This is the first money to flow in to Reel Streets, up until now it has always gone the other way, at the rate of about £750 a month .............. quite a lot to spend on my hobby ................. just don't tell Liliana, 'er indoors!!!
John