We reported that Developers preview running Lumia 1020, Lumia 1520 on AT&T and Lumia 920 on T-Mobile Germany started receiving Lumia Cyan update. Add Lumia 1520’s UK country variant to this list, as announced in Windows Phone support forum.
Joe Belfiore has confirmed that BitLocker issue has been resolved, so go ahead and try to update your devices OTA for Lumia Cyan, if it is one of the devices mentioned in above screenshot.