If you have not spent any time on the slopes before then we definitely recommend a couple of lessons on the indoors slope , give The Hemel Snowcentre a call and you can get a discount via coolskijobs.com
If you are heading to work in Europe (or the Swiss alps) then you should look into taking an EHIC card with you to cover some basic medical needs, however this is a changing situation due to Brexit, but we doubt this will affect us until at least 2018.
If you are working for a tour operator / chalet company then check their insurance cover, importantly this is all about your slope time, but also check that you are covered for theft / accidental loss etc
Have a look at French SIM card deals, these can be found on ebay or on the actual French sites, although there are more opportunities to use your UK number abroad at no extra cost
Bring cash and a card with you, you may not get paid for a while plus if you are working independently then you will need money for a ski pass.
Always take a stock of Lemsips/cold tablets /pain killers etc with you as this kind of thing is much more expensive in resort and you may not have a pharmacy to buy them from.
Bring a bag of wine gums in case you bump into me 🙂
Plug adapters… Bring them… Or a 4 way English adapter (with a surge protector)
Driving licence as you may need to show ID / hire a car etc
Ensure you have all your internet banking sorted before you arrive.
Make sure you bring warm clothes… Sounds daft, but you would be surprised.