i was chatting with clodagh about this a while ago and she said that although she's with a few agency's she gets the vast majority of her gigs through her own website.
with what you said about emailing promoters, it's easy to ignore emails. try and build a friendship through email or phone, then maybe post a mix cd then broach the subject of gigs.
i dont know what its like for promoters but i get sent shit loads of links from people who i don't know with little more than 'have a listen'... or words to that affect. i think **** em, if they can't be bothered to first make some kind of contact and build a friendship then i can't be bothered to listen to there music. also if possible send well labelled mix cd's... who can be arsed downloading mix's they take ages. it's all about looking professionnal