Some friends of mine own a C210 Silver Eagle. (Allison 250 turbo prop conversion of P210)
We have been to Corchevel several times direct from strip in Berkshire. About 3 hours IFR at F200 ish.
Not a trip to depend on, due Alp weather, has to be VFR arrival obviously, and can get stuck there if no hangarage and de ice available.
Great when conditions permit.