Many thanks to you all for the advice.
It seems that true award space might be very limited on the when+where of our intended hols and will need to use the (probably relatively poor value) cash+Avios option for the core tickets on BA metal. I wanted the right tool to check that there were revenue buckets available for the GUF2 for me to call to upgrade (probably BAH inc car).
Many thanks again in anticipation of advice for Seatspy or EF to do this