In case anyone's interested. :-)
Kat was right, it was a partially constituted mime encoded message (the actual
mime headers didn't make it though!). I recognised the encoding as "base64",
and, if you've got Linux you've probably got a utility to decode it:-
Save the "gobbledy-gook" to a file (say bonnie.txt), then:-
mmencode -u bonnie.txt
and you will see the message.
Cheers
Deri
PS I hate computers!!!