A small update with build number 18.3.1.C.0.22 is currently rolling to Xperia M2 (D2303) and Xperia M2 Aqua (D2403) customers to the Vodafone network in Germany, Spain, Netherlands and the UK.
The previous build number (18.3.1.C.0.21) brought Android 4.4.4 KitKat to the Xperia M2 including a fine-tuned camera, as well as improved battery, stability and system performance. The latest build number likely only makes small bug fixes.
