Mike,
Arnage is definately worth a visit, although whether or not it's walkable depends on how good a walker you are. It's quite a hike, but as the weather was good last year, it was total gridlock on Saturday night, walking would have been quicker. Take some whiskey.
H
Take a bike is best. Not much more than 10 mins from Maison Blanche.
Viewing at outside of Porsche curves is excellent. Access via public road - so no cars within sight along the way.
Don't mix whisky and bike, though. I did once, and ended up with a broken collar bone.