I'm meeting a friend and want to treat her to lunch in London as she has been very kind to me. She earns a LOT more than me and has quite refined tastes, but will be impressed by anywhere on trend or of the moment. (E.g a million years ago when I lived in London and had my finger on the pulse, I took her to Jamie Oliver's Fifteen, which was new and she loved, and another time a wander around Spitalfields market.)
She doesn't live in London so it's unlikely she'll find somewhere tired or clichéd.
Budget ideally around £30 per head for lunch (excluding drinks). Ideally central London, accessible by tube. Any ideas?