Looking at this you could be forgiven for thinking that you were beside a Paris Cafe. Instead, we have just walked up to Sloane Square, and found Cafe Oriel. This very french style Bistro serves excellent coffee (and for that matter, citron presse). Being where it is, you have an eclectic mix of people and you can use it for celebrity spotting if you are so inclined(I'm not).
However, if you want to feel like a real Londoner, make the trek there one Sunday morning and sit with a coffee and cake, reading your paper and watching the world go by.