Just a quick update - here's something on another site that suggested a DDM swap-out worked fine (as that's what I'm considering). The OP then posted again at a later date to redirect another user asking a similar question to the post - it appears he gets his car serviced (and hence software updated) and hence it seems that swapping the DDM in this instance may have worked without issue...
OP:
http://www.matthewsvolvosite.com/for...ic.php?t=23510
Follow up post:
http://www.matthewsvolvosite.com/for...hp?f=9&t=26624
Just more examples of people having swapped bits without any mention of it hosing their Volvo...! :-)