Oh, just discovered something...

When you press the power button, nothing happens for about 5 seconds
(bootup). After this the buzzing happens. HOWEVER, the buzzing is at
two pitches and changes at ~2second interval. At the same time, if I
look down the back, theres a red LED that alters in intensity in time
with the buzz.

I'm assuming then that a startup 'test' has failed, and that this is an
indicator of the problem. I'll open the back up this weekend and see if
theres anything marked around the LED that can indicate the exact
issue.

Hope that may help anyone in the know - I'll also update this thread
just incase it comes in handy for anyone else out there on the
interweb.

Ta!

Danabnormal