Trains: 0715 Manchester Picadilly to London, 10:25 Eurostar to Paris and then 15:42 Paris to Oulx arriving at 2005. Or leave Friday evening and try the comfort of the Luneas night train to Briançon, arriving on Saturday morning. You can book tickets at Rail Europe.
Driving - French motorways are notoriously quiet compared to our roads, which makes for fast, stress-free driving. It's an 950 mile journey and would take about 18 hours. At a cost of around £500 return with a car of four, it's a flexible and cost effective way of getting to the Alps. Don't forget snow chains or socks though!