I was once stranded in Picton for 2 days. Believe me, no buses go there lol. Also, every mechanic closes at 5 on Saturdays and doesn't open on Sundays. Definitely something to keep in mind if you rent or borrow a van from someone.
If you do get stranded, I recommend the Sportsman Motel. Comes with complimentary "Don't gut your fish in your sink" signs.