I Need to try and extend the battey life of My HTC One as much as posible. Can anyone recomend be it free or chargable some power saving apps to try ?

beware most of the battery saving apps turn off 3g

you don't really need an app - just turn down the brightness, turn off wifi, 3g, Bluetooth when not needed.... close apps that run constantly in the background waiting for push notifications, such as facebook.

There is an app called Watchdog - there is a free version, but I went for the paid one as it was only a couple of quid.

I got it to see if anything was hogging the CPU - which there was not apart from some part of the OS (Android media player or something like that).

The best battery saving app is Snapdragon battery guru from Qualcomm. It is free. Of course you need the right processor, but you have that in the H1. The app monitors your use for three days then it shuts off the stuff you don't need. It is really really good. Give it a try.

Greenify

LLama can be set up to automatically turn off e.g. wifi/bluetooth when you leave the house/office.
https://play.google.com/store/apps/d...Llama&hl=en_GB

I've found Llama to be a bit unreliable. I use Setting Profiles to do things like trigger a work profile with no wifi or gps when I'm at work. Can be based on locations, calendar events, times etc.

Which requires root. There is no reason to root just for better battery life.