Thanks for all your responses- I was concerned because I had bought a bit of 0000 and 000 only to be told that they would be too small. From the sounds of it, I think I may be on the right track.
Thanks Antheia for your correction. I checked my notes from the Birth Clinic and the radiographer (?) (person who did the ultrasound) has written 8.5 pounds (4500g)?? I am not sure what she meant now! 9lb14oz is quite different to 8lb!