In reply to gimmergimmer:
If your back will hold out that far, when I was knocking off Munros (20 years ago!) we often used to camp at Strathfillan Wigwams between Crianlarich and Tyndrum. I've just looked at their website and it looks like £20 a night to camp. Back in the day there used to be a communal kitchen for campers. Good place to watch the West Highland Wayfarers limping along.