I would agree with most of what cbdo says except for one point: In the end you did get a new timing chain and slides. For this you owe the shop due recompense.
On the other hand the shop did cost you a great deal of time, effort, and stress. But for this you got a valve job. I would say that the right thing to do is to pay for the chain and let the shop give you the valve job for your trouble. This would prove to the shop that you are a 'stand up guy' (which is important to some people) and keep the shop's door open to you should you ever need their services again.
Paying for the chain would, to me atleast, calm the waters and clear the air between you and the shop. If not cleared up the animosity that has been generated will remain a stone in your craw, or a burr under your blanket, depending on what part of the country you are from. Besides, you were already prepared to spend the money for the chain.