Checked elsewhere on Internet and appears to be a duff battery - Returned battery and may or may not get a new one (ie this link ends here unresolved I'm afraid - I shall just run on AC power when I need to use it which is rare anyway). Thanks for contributions to date 
Its ancient I know but still going strong - except this. Worked on AC but battery would not take a charge. Purchased new battery on Amazon and now it recognises battery, has charged it from 3% to 96% so far, no orange light but if I disconnect AC cord it powers off immediately. Have reset driver for battery control, reset all settings, changed bios battery, run diagnostics (nothing found). removed battery, held power button 2 mins, rebooted. All to no avail, only thing that has changed since I replace battery is that the amber light doesnt come on, and the battery charges and shows good charge. Any more ideas or are we looking at some sort of duff battery issue?
Inspiron 1564 Only Runs On AC - Wont run on battery