melaniedc &
Singingheart I have / had the same problem and I really appreciated all the help given by experienced pilgrims. It really comes down to personnel preference, all well and good if we've been on the camino ourselves, but being a novice it's not always easy to decipher the advice given and come out with a solution that fits.
Today I spent some time in my local walking shop discussing this very issue, I had a look at a lot of sleeping bags and the lightest ones are the mummy variety which I can't stand. The lightest rectangular one that I could fine was 1.25 kg, not a bad weight if you're not carrying it far. Then I looked at the liners and was very surprised at the size and weight. I ended up buying a silk liner that weighs 1.25g and fits in the palm of my hand. I've also opted to take a set of very lightweight thermals in the of chance that it might be a chilly night on occasions.
Should I find that this system doesn't work then I'll be hunting the shops for something more substantial.
Hope this helps.
Singing heart, I m right be leaving a day ahead of you, but I'm very slow unless there's a beer on the horizon, I'm staying in the Beilari on the Saturday night.
Been Camino.