I've re-read this a couple of times and had the charger set up for a couple of hours. In a dimly lit room the LEDs can be seen but are not bright. If I take the TSU6000 out of the cradle the lights stay on and are the same intensity, which I believe is dim. So, I conclude (possibly wrongly due to lack of experience) that power is getting to the base but nothing is charging.

The battery is now so flat it wont respond to touch or movement, however I found that if I unplugged it and replug it in the TSU6000 will respond for a short while.

Could it be the battery not holding charge, or a problem in the base? Any futher diagnostics suggestions or advice would be appreciated.