Now seems to be bookable. Not sure from when but I was looking at London for Feb/March next year and its available. Also some room images on website. Seems like a significant number of small windowless rooms with "ok" rates (I saw around £120) but really climbs for "proper" rooms. Not feeling terribly tempted. I enjoyed my stay at the Flex Euston, and can get the larger corner double for about £150 which I will probably go with.