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!!!