SEO web content writing (short articles)

We need high quality English (British) content writers (or companies) that are experienced in SEO writing. All items should be written using a given list of keywords and under a strict format. We need 900-1000 items before launching our website and then we will need weekly updates. The subject of our site is "online Bingo". Price = $0.75 per item. Content item = a short and summarizing description + headline + 175-200 words. Timeframe = 20-25 items a day.