Hello mate...
I was going to do just that......BUT....
By 11am today it was down to 43%, no usage apart from a quick factory reset, in the hope that would make a difference. 2 hours later it was vibrating, so I thought I had a call (Lucky me right?!) it was basically telling me the battery was DEAD and switched itself off never to be seen again HAHA.
I have come to the conclusion that it must be a dud battery, or perhaps the device. I called o2 just now who said they will send out a phone straight away (fair play) but no blue ones in stock just yet! The phone is back on charge so not muc point in me posting batt stats now sorry. My friend with the same phone had 79% battery with alot of screen play when I had 43%...... make of that what you will but something is not right.