OK, thanks so much for the suggestions so far - I'm geting a bit closer:

I've set up a PAN with DHCP on my Windows box, set up the dummy 'DEFAULT' internet connection on the 770 and got paired and connected by bluetooth.

It seems (by observation and according to the tutorial) that the 770 can't pass the DHCP stuff through to the dummy connection (shows "Default router: 0.0.0.0" in connection manager).

The tutorial then goes on to explain how to set this up manually - this is where I'm stuck

I tried to install the ARM compiled ping package from Debian, but it fails saying "Unable to install inetutils-ping. Component is built-in.".

I tried my best to find it on the device, but as far as I can tell, it's not there.

Now I haven't yet managed to become root - could that be the cause??
(don't have a suitable Linux box, haven't managed to get my Mac's command line to see the 770 on USB in order to flash it, even though it shows up as a drive on the desktop... but that's something I need to post about in another thread!)

(as an aside, I had the same problem installing AbiWord at one point - but then found a different .deb that worked OK - could these errors be a hangover from the original Debian that was stripped down to become Internet Tablet 2005 OS?)