Hello Aiden,
Have you looked before to some of freelancing sites? If you did'nt please have a look. You will get some seo companies with proven tracking records. You can make your proposal within targeted budget.
Elance and Odesk are the best. You have to sign up as job vendor in order to posting your proposal. A good number of skilled seo will be bidding against your job offering. So will be able to pick the best one who will be best fit for you.
thanks