I agree on the branding (doesn't sound like its about London startups) but having seen this site for a couple of weeks now there is a nice little community there. It makes sense to create a subreddit or site for London startups as there's a big community that doesn't really have a (non-facebook) forum to communicate and share.
Because HN is very SF centric and I know the London comunity will really benefit. Quite simply really. Not trying to create a $B company just something good for the area