I made it using No 10 thread for the padding cord and No30 thread for the crochet working. It made this butterfly come out at a reasonable size at 13x14 cm.
I find that working with the larger guage thread when tackling a project for the first time makes things a little easier, having said that this particular motif took some time and effort to make.
The pattern called for a "mesh" which I cannot find any useful references to on the internet - it would seem that they must be some sort of circular form to wind the padding cord onto for creating the padded rings etc. I'll keep on searching and see if I find any more information on this.
In making this motif I learned the valuable lesson of keeping the padding cord tight & pulling it up from time to time. Particularly when I was creating the edging that goes around the whole butterfly the padding cord bunched from time to time and it needed to be pulled through to flatten it ... I had to rip back a couple of times when I had gone too far to pull through successfully. Like I said - lesson learned!