Check out Brixton Cycles (they're in Brixton surprisingly, right next to Stockwell skatepark and near the Brixton Academy) and while that's not in any way North London, they're good and they stock Surly.
Brick Lane Bikes - BLB - sometimes get a hard time on here, but they've got pretty decent stock and they know what they're talking about - although I have seen some ugly conversions in there. They have Bob Jackson Frames at £350, which while that's £50 more than Bob Jackson themselves, you at least don't have to wait eight weeks to get it. Maybe ask your 'dumb' questions on here ; ) before you go to BLB, and don't go at weekends if you can help it.
Check out Brixton Cycles (they're in Brixton surprisingly, right next to Stockwell skatepark and near the Brixton Academy) and while that's not in any way North London, they're good and they stock Surly.
East London, Fixed Gear London (http://www.fixedgearlondon.com)
or
Brick Lane Bikes - BLB - sometimes get a hard time on here, but they've got pretty decent stock and they know what they're talking about - although I have seen some ugly conversions in there. They have Bob Jackson Frames at £350, which while that's £50 more than Bob Jackson themselves, you at least don't have to wait eight weeks to get it. Maybe ask your 'dumb' questions on here ; ) before you go to BLB, and don't go at weekends if you can help it.