A bit more research, i'm not alone with this problem.
Fixes are wide ranging from the obvious to the ones linked to by Craig.
Latest one for me was to do a hard reset of the device, basically, hold the round button and the on/off button at the same time until it restarts.
Also a recommendation is to uninstall facebook and reinstall it
If this doesn't work i'll be totally resetting the device when i get home and if that doesn't work i'll be asking for a replacement handset, if no go then i'm gonna do the same as Rob and get a Windows 8 phone.
As much as i very much like the iPhone i'm totally fed up having to recharge twice a day..............
I have to admit, my S5's battery is way better than the S4. I always leave it charging overnight next to my bed and only unplug it in the morning. By the end of the two years of my 4S I couldn't really get through a full day without having to charge my phone. Most days my 5S is still showing 40% to 60% of battery left.
It's difficult to get a proper comparison though because I changed to Vodafone (from Orange) at the same time and Vodafone's signal is utter crap - significantly worse than Orange in every location I've used my phone so far. And a poor signal - especially if you're phone is constantly trying to find or use a poor or non-existent 3G signal - is the worst possible drain on a phone's battery.
R60 Light White / Red Countryman All 4 John Cooper Works Auto
R57 Chili Red Convertible John Cooper Works Auto
Yep I moved a way and got the nokia lumia 1020 windows phone it's very good battery last a day easy like it a lot nice big Screen as well
New sig coming soon
Since i did the hard reset my iPhone has significantly improved, tonight will be the big test, anything less than 60 per cent drain on standby will be a big bonus
Overnight test, 40 per cent battery drain, but, it's constantly searching for network, anyway, well happy, so, anyone else having similar problems, try the hard reset.
Today i am gonna let the battery run down completely and then recharge, which was another remedy advised online
Finally was able to let the iPhone run out of battery, even to the extent trying to turn it on again a couple of times to ensure full drain.
Recharged and did the overnight test again, wow, significant result, now only a 14 per cent drain overnight.
My advice, hard reset and then do the battery drain