Just keep it as simple as you can. You are always, somewhere along the line going to get cancellations at the last minute for for genuine or false reasons. It's life. S#it happens.
I have never had a face to face quote cancel. I must admit, I have had some phone bookings cancel. However, I always call the customer 24-48 hours before the job to confirm the booking. From experience with taking phone quotes, you sometimes get the feeling that something is not quite right with a prospective customer, that is when you double check.
Anyhow, how are you going to make them pay the cancellation fee!! Send the boy's round to sort them out!!! I don't think so. Forget it and move on. In twenty years in this business, I think I have only turned up to a no show about 5 times. Firm up your jobs before you travel. You can bet, the one's that let you down, are the one's you have to travel the furthest to.
Jim