There's a bunch of bike shops I use. The closest one is just across from the library where I tend to take my son on Saturday mornings, so I'll sometimes pop in there if there's something small (in size) that I need to pick up. However, although they can give some fairly good advice the main guy there is rather abrupt and prone to give you a withering look if you're not obviously rather knowledgeable about bikes, so they've fallen rather out of favour with me. The next one is Finsbury Cycles near Finsbury Park tube station, and is the shop I got my bike from. They're very friendly in there and are the place I go if I need something done to my bike that I can't do myself. They're also not that far off my commuting route, so I can sometimes pop in on my way to or from work. Also directly on my route is a Cyclesurgery, which is open until 7 two days a week, so I sometimes pop in there on the way home.
I've got an
Evans Cycles close to work so I can pop in there at lunchtimes, and they've got a bigger selection of stuff than the other shops I know. Also close to work is
Velorution which is great if you happen to want something a little unusual, like rainlegs. BikeFix isn't far off my commuting route as well, so I've picked up a stand and handlebars from them in the past.
I guess I do pretty well for bike shops!
I do order some things on-line, but not much so far (just two lights and a child trailer).