Winner of my 'best burger in London' award goes to Meat Liquor. Ignore reviews complaining of crowds; go either on the dot for opening, late at night, or for lunch. The dark corners are perfect for cosy-ing up to someone special while devouring some crazy good meat. Have the chocolate cream pie.
Meat Liquor - This is near Bond street and heads up - no reservations accepted so there are often queues (everyone likes queues on wednesdays). A few friends have gone here and said it was worth the wait - for both the meat and the interior. This is a link to a review with lots of good pictures!!
Meat Liquor is not big on utensils and the decor may not be everyone's cup of tea, but the burgers/wings/chips/drinks are beyond reproach! The onion rings are legendary! Show up on time at noon to avoid the long queues.