First I would like to admit that I really am not an expert in this regard at all. I am not the biggest fan of clubs in general and I don't actively seek out dubstep music. My entire exposure to dubstep has been involuntary. And while I am sure I am working with a weird sample (it isn't really fair to extrapolate 9,000 college students, most who aren't even from Britain to represent the tastes and knowledge of the British music populace) most of my fellow students at LSE know nothing about dubstep itself. They actually all thought it was American (they wish). The only people I've met at LSE who like dubstep are the WASP-y Americans that basically make up my entire study abroad program. It is definitely big in London though, just not among the student body at LSE. Overall, I haven't gleaned much good information about the genre from my classmates though.
I guess I have made enough excuses. As I told Tim, basically the only thing British college students do is go to clubs, normally during the week. At said clubs DJs play horrendous music that people dance to (and if the club is expensive enough they will also take ecstasy while dancing). There are some hipsters in the country, but they are mainly old. When I saw the National the first thing I thought about was what a boon the concert was to the British babysitting industry. Fun Fact: British hipsters don't wear flannel. Based on empirical observations at the Tate Modern Gallery and the National concert. So basically, club music is huge, and all genres of dance music (besides the good ones (Four Tet, Aphex Twin, Chef Boyardee)) are big among British youth. So basically, while dad-rock and twee/indie/baroque pop/chillwave/c86/witch house (actually that last one isn't true thankfully) are popular in London, they aren't at LSE or among the general London student populace.
Garage is probably the first dubstep-ish genre. Its similar to house music. The drums here are very house-ish.
Like all of these moronic genre distinctions, there is tons of overlap between garage grime and dubstep and everything else. The Streets was a Pitchfork darling back in the day and incorporates a lot of garage elements in his music. He has these ambitious ideas and concept albums which is definitely refreshing but his phrasing is incredibly awkward on basically all of his songs, especially on his material after Original Pirate Material.
http://www.youtube.com/watch?v=0Z1kRhiPE0E Basically garage sounds a lot like house with some rap elements. They don't flow like American rap artists though. I have noticed that British rappers in all of these silly subgenres have no flow whatsoever and kind of just throw in their lyrics wherever they see fit with no real logic behind their decisions.
Grime predates dubstep and is the closest thing to American rap music I guess. I haven't heard any British rap music that sounds like American rap (fast tempos, dense beats, (somewhat) intelligible lyrics) and grime and garage are the closest. Dizzee Rascal is probably the most popular example of that. Pitchfork was all over Boy in Da Corner when it dropped in 2004. It is honestly probably the worst album I ever bought. I tried really hard to get into it before I went to London and I just couldn't do it.
http://www.youtube.com/watch?v=YH0KWX2a8zY This song highlights the terrible "grimy" bass that is in grime and garage songs. Everything is pretty sparse as far as production goes.
Tinie Tempah and Tinchy Stryder are also huge in London.
http://www.youtube.com/watch?v=cMg5cQd5f50 This actually sounds a lot like commercial American rap with the hook and everything.
http://www.youtube.com/watch?v=3wpCf0FsZKQ This shows how much the British like that dirty grimy bass sound and generally bare-bones production. It also showcases the complete lack of lyrical coherence in most British songs songs. British rappers also love vocal manipulation just as much as American ones.
Then there is dubstep. I think it grew out of grime, garage, and dub. I have also heard it applied to virtually every electronic artist and it seems people are careless with classifying stuff as dubstep. I will go by the definition given by clubs i.e. stuff that is played when the club has a dubstep night. It has the same dirty grimy sound as garage and grime especially when it comes to the basslines. Most of the songs aren't that complicated. And that whole ambient-dubstep sound that Burial is big on is not that popular. Burial is not that popular at all here compared to other lamer more dance-friendly dubstep artists.
http://www.youtube.com/watch?v=UYwKCuSh34c&feature=player_embedded This is pretty drum and bass and faster than what I considered dubstep before I went to London but it apparently falls under the umbrella.
http://www.youtube.com/watch?annotation_id=annotation_717554&feature=iv&v=_rbA56VdVo0 Note the generally lethargic rhythms and how every song sounds the same.
And then there is electro house. I would say that this is the most popular genre among my British contemporaries. Swedish House Mafia, Deadmau5, and Benny Benassi are the big names. Its really repetitive music that has pretty fast tempos. It leads to actual dancing instead of the wobbling preferred by dubstep listeners. Revolution 909 by Daft Punk also falls under house (probably electro house too). There isn't that much overlap with the dubstep family here. LSE has a club night on campus and I went once. This is the kind of stuff they play. Miserable experience. Its basic trance and house stuff.
Don't ask any British people to check me on this. They will undoubtedly say I have no idea what I am talking about.
Moral of the blog post: If you find yourself in London, buy large noise-eliminating headphones and avoid clubs. Don't wear flannel to hipster concerts.
While your question suggests otherwise, if you or anyone at Larry David are interested in quality electronic music, I recommend listening to this song. It reminds me of Pogo, Four Tet, and Koushik.