I need a good copywriter

I'm looking for someone able to write articles, information for web pages and blog posts. This will require research and good copywriting skills. Most of this will be done to a formula/structure for how the articles are to be written, largely coming from a marketing background, rather than a technical English background. That means more conversational English, short sentences, short paragraphs, and our style in format will be proscribed, so you must be able to follow directions.
The subject matter will be varied across a range of subjects and industries, not too technical but some product descriptions will be required. While this will start at a low level of work (maybe 1 to 2 assignments per week) it could grow to 5 or 6 regularly. Must be able to work to a tight brief and agreed deadlines. We won't require very fast turnaround but the deadlines will be cast in stone.
We will require samples of past work and a paid test assignment will be part of our selection process.
I'm a business coach working with SME business owners who has clients who need a reliable resource. The articles will be 400 - 500 words in length.