http://www.techradar.com/news/xbox-one-x-deals-price-bundles

Update: As expected, Microsoft has announced that pre-orders are now open for the Xbox One X on their Gamescom livestream, as well as announcing an limited edition Project Scorpio edition of the console. 

So far only a limited number of retailers opened up their pre-order pages and most of them sold out promptly. As things stand today only Argos' Xbox One X pre-orders remain now in the UK, so don't wait too long if you want one on launch day.