Hi, Sue,
I have a lightweight sleeping bag Snugpak 750. I am going to buy a new one this year because it's 10 years old and I'm always cold in it. But I am what the Spaniards would call a friolera, meaning I'm always cold (if anyone has a good word for that in English, let me know!). I wore lambswool gloves for about the first two weeks on the Vdlp, till 10 in the morning or thereabouts. And I almost always used an extra blanket from the albergue on top of my bag. I remember that in Zamora, A Gudina and Laza the hospitaleros had already put away most of the blankets for the summer, but I was always able to get one. I think that shows, though, that I must be unusually cold!
So I guess there is a lot of variation and you should figure out where on the scale you fit and plan accordingly. But as I said, extra blankets seemed to be plentiful.
Buen camino, Laurie