A 50c handling charge is more than fair. We sometimes have a $5 handling charge for really bulky products. As a seller, you have been upfront with costs. The buyer should have no problems re-delivery charges as they have accepted this when they confirmed their purchase.

You will bump into some very miserable people in retail. I woud agree with you that it is probably not worthwhile to have them as a customer. Imagine if something beyond your control went wrong? i.e. couriers dropped the box. They'll expect a Royal pumpkin carriage at their door step to escort them to a Ball where they are to be publicly honoured with a replacement and full refund.