Why am I having problems with new update to T- Mobile LG G3 (UK)?

[AC Question]

I had an update a couple of days ago and the build number has changed to LRX21R.A1439960697. It's made a complete balls up of my phone. Something is running in the background and I don't know what it is (except Google Play Services), the phone is constantly warm and absolutely draining the battery. And some app's just don't work, and my widgets are all playing. Pulling my hair out here not being able to fix it.

Has anyone else had the same problem recently? Or any idea what I can do to fix it?

Cheers, Scott.