You no longer need an agent to submit to this mainstream publisher
Tor UK is the Pan Macmillan imprint specialising in science fiction, fantasy and horror. They also publish some YA crossover fiction and novels based on computer games franchises. Their writers include international bestsellers like Douglas Adams (Hitchhikers Guide and all round genius) and James Herbert (scary stuff, very scary stuff).
They have just (January 29) announced on their blog that they are now willing to accept direct submissions. Click here for more info but this is what they are looking for.
Complete and unpublished science fiction, fantasy and horror novels, written in English of between 95,000 – 150,000 words.
Submission is by email so no printing or postage costs, but just because they have made it easy don’t let anything go out that is not your best possible work. If they say no, then it stays no, even if you polish it later and make it perfect.