H Lizzy I ski each year in France, few things to think about..
Reduce basal by a third, eat a good breakfast each day, say porridge, reduce bolus ratio also for breakfast and lunch if skiing all day but watch out in the evenings as bg can start to rise then.
Keep your blood glucose monitor close to your skin, it can show error messages if too cold, I put mine under my thermals. Try and test each hour on your first day to build a picture, if your really high up then use the lift shelters to test in as your hands can get quite cold.
Hypo awareness reduces at high altitude, so testing is essential, I've had a few hypos and had no idea.
Jelly babies is the best hypo treatment
Have a lot of fun and stay safe, I did my first black run whilst dka, definitely never put me off !!!