Just an update:
I spent many hours last night working on my phone, and after leaving it on my docking station for a few hours, it had enough battery to turn on, though it was only a tiny bit of battery. I quickly plugged it into my PC and was able to load the backup from iTunes from about a month ago, so that it was now my phone again. However, straight away the battery died again, and I left it on the docking station all night, but it never charged. Now it no longer shows the battery sign at all, just a black screen.
Any help at all would be greatly appreciated, as i was checking out the apple website, and as my phone no longer has warrantly it's going to cost me £125 for a service which ain't cheap!
The problem is most likely dirt or moisture in the dock connector on the bottom of the phone. Might also be a bent or damaged pin. Get a good magnifying glass or jeweler's loupe and inspect the connector carefully. Clean out any dirt or lint, and inspect for corrosion on any of the pins. A new toothbrush is a good tool for cleaning, or an air blast can. If any pins are damaged you will have to replace the phone for £125, or go to a competent repair shop and have the connector replaced, probably for less cost.