This has become my favourite haunt to do freelance work. The staff are always friendly, the cookies and brownies delicious and they do a wicked range of smoothies. Importantly for freelance work - the WiFi is reliable and there are usually tables available near power sockets if you need to charge your laptop. The front is opened up in warm weather so it comes pretty close to working on a terasse, plus you get all the theatre of Kensington. ;)