Right then, I was the one who originally posted this topic.
I ordered a new battery, as It was getting ridiculous the amount of time I was getting with the battery. The new battery (which was exactly the same) gave me approximately 50% more power!!
Im with Orange UK, called them, explained the situation and within 2 days they sent me a new one (which I have yet to use) and I will send the old one (the one that was initially shipped with the phone) back to them in the jiffy bag (freepost) provided.
So this proves that some batterries can be faulty. I would suggest, if you suspect that you're not getting as much power from your battery as you think you should, you change it.
However, I still need 2 batteries for a days (18hrs) usage - moderate to heavy usage - gps, internet etc etc