Cut paste from Sony Forum :
Rickard Sony Xperia Support
Aug 25
In June we received reports highlighting excessive battery drain on devices running Android 4.4.1 or higher - and identified that the root cause was related to the latest version of Google Play Services (4.4.52).
Google released a fix through an update for the Google Play Services app – it has restored battery consumption to normal levels in the following devices: Xperia Z1, Xperia Z1 Compact, Xperia Z Ultra, Xperia Z2, Xperia Z2 Tablet and Xperia ZL2.
For Xperia Z, Xperia ZR, Xperia ZL and Xperia Tablet Z, Sony Mobile is preparing an additional correction, which will be delivered in an upcoming software release - this release is now undergoing final stages of testing and will be available shortly*.
We encourage all users to update the Google Play Services app regularly to ensure normal Android application, service and device functionality.
*All software release dates are dependent on local and operator approval and release times may vary.
We just need O2 to hurry it through!!