So far it seems '170 has the best idea so far.
Granted....flying the old darling home is the right way despite the things that argue against it. Bell 47's have been doing mountain flying since they first appeared on the aviation scene (the Bell's that is....). Following a road through a high mountain pass is not all that hard....minding the wires and masts and such. Yes it can get windy and bumpy....but at least you should be able to pick your day with some leisure.
I would pick the lowest, most flat, widest open Pass possible....and look for the least amount of mountainous terrain for that part of the trip.
English Channel water is pretty cold this time of the year is it not? I bet it is colder than the bottled water sold in the Ferry Bar!