I could recommend someone if you're based in the UK, otherwise I can only give you advice: make sure you know exactly what they will provide before you hand over the money - make them specify which search terms they will get which rankings for in which search engines; also don't pay for search engine submission. search engines will naturally index your site when they index sites which are linking to it. directory submission isn't so bad but don't pay much for it. better to pay to make sure you're site is keyword-optimised and well coded for
seo, and then pay for link building from popular websites and from websites which are directly relevant to your industy.
hope that helps :p