Thanks for your reply. Online I found a video of someone removing a plate underneath the keyboard. Sure enough I spotted the cmos battery under there. I have replaced the battery but this has not helped much. Just as before I changed the battery, I can sometimes get it to start booting up but after a few seconds all LED's will go off. Sometimes to be replaced with a flashing amber battery LED.
Just once this morning it fully booted up into windows. I left it just running for a few minutes then switched it off to see if it would start up again. It didn't. Several more attempts have also failed.
To answer your question - With the laptop switched off, if I plug in the charger the battery LED turns on steady amber.
A possible clue. Often when I press the start button the left hand green LED (near the handle) will come on, along with the 2nd green LED indicator from the left of the row near the hinge. This is not the hard disk access indicator, its the one to the right of that. Its symbol is a tiny rectangle with what might be a small arrow pointing left. Very hard to tell, its so small.
The fact that it did just once fully bootup into windows gives me hope but there is still clearly something wrong.
Any ideas?