Soldering Power To The Main Board
After about an hour of fiddling around managed to solder the 4 wires which will take the power from the external socket to my board and back. The solder on the machine is lead and it does not want to melt. I had an absolute nightmare getting the wires through the board and getting the solder to melt on both sides. Finally after lots of fiddling got the wires soldered on.
Next tested that it actually will work from the battery. Machine initially kept powering off after a few seconds. I found the reason, i'd managed to short two of the connections on the back my perf board. Sorted that out and it works ok.
Next thing to do is cut the tracks so that the input wires are separated from the output ones, the input will power the charger and the VGA convertor board. The power from the battery board will then go back into the machine (or be powered via the input if the switch is in the correct position).