Thanks for the replies. Not sure what best to do here.

I have called them back having found some award availability on AF/KL, expecting that they would be able to rebook this ticket and they are saying whilst there is award availability they cannot use it as my flight was booked with the companion voucher (into class 'G').

If this was a BA award cancellation then they would rebook into a revenue bucket on another partner, however the agent said that VS won't (after speaking with supervisor) because of the companion voucher.

With regards switching this to a LHR departure - they can move the revenue ticket to MAN-LHR-JFK on BA/VS, but the award ticket can only be changed to LHR-JFK.

If I book a single positioning cash ticket MAN-LHR for the award pax to complete the full itinerary, am I running a big risk in the event that there are delays or domestic cancellations? Are Virgin likely to show flexibility to move us both together to later flights if a BA delay/cancellation results in me misconnecting at LHR?