Kat B.
Yelp
This is the first gallery I went to as a new resident to London - and, as a total street/guerrilla art enthusiast, I was really impressed.
The gallery is in East London's bustling Brick Lane, sitting quite contentedly in a dank, graffiti-covered alley that on gallery opening nights is filled with hip-looking young folk (many who are also surreptitiously brandishing paste-up materials and paint pens, bent on tagging every open space when no one is looking).
The night I went here was the RSVP preview of Stolen Space's "Wild Fantasies" show, which features several posters of the "Dont Panic" tradition - many of which were created by our generation's most well-known street artists, from D*Face to Banksy to Shepard Fairey of OBEY/Obama poster fame. Free drinks abounded and the place was packed to the rafters.
Overall, it's obvious that this gallery has a true appreciation for the ethos and philosophy behind street art - many of its founders are street artists themselves. Squabbles about the rammifications of the commercialization of street art aside, this is a reputable spot to sample the work of respected urban/street artists with a political, street-originated bent.
A tip: be sure to grab a Don't Panic promo package on your way out. They're free and distributed around the city, but this gallery is the source. They're filled with flyers and posters for London street/nightlife events coming up.