In reply to connor:
> I was thinking a down bag that goes to about -25C? I am envisaging bivvying before some of our bigger objectives, the bag will also be used in Scotland in winter, PHD do some nice bags that look more suited to alpinism IE with a Bivvy cowl, but i also like the look of the Montane deep heat bag.
-25 sounds a bit extreme for the Alps in March, unless you run particularly cold. I bivvied at 3000m in Sept in a Phd minimus (rated to +5). It was a bit chilly but I should think something rated to -10 would be adequate.
You might also consider a half-bag to save weight, if you're going to have a belay jacket anyway. I believe PhD do these.