Small restaurant on Highbury Corner that started off focusing on (basically) posh kebabs, but which is now producing some of London's most innovative dishes, focused around unconventional meats, cuts, and breads. Not often you can eat incredible food while listening to heavy rock and metal, but Lee Tiernan has nailed a winning formula.
Leila McAlister's grocery shop and café off Arnold Circus, Shoreditch. You can find the best of everything, from jars of horseradish to eggs and croissants.
If you want a peaceful day out of the busy city, Highgate doesn't really feel like London. The cemetery is interesting and peaceful, there's a tour of the old half which is definitely worth the money. Karl Marx, among others are buried there.