Here's an interesting photo that I'd not seen before today. Obviously 'A' is in the middle, but I don't recognise the other two. I am tempted to say that I think the picture must have been taken down near the embankment on the north side of the Thames and that beyond the cranes in the background, we can see Big Ben. That would be my guess anyway.
I'll guess that the other two girls are models, although I had briefly wondered if the blonde one was Rosemary Donnelly, but I don't think she is. Probably a promo shoot for either the series itself or the fashions.