As regards the part that failed, I was initially told (by the garage that did the job) that the drive chain had broken, but I thought this model was not chain driven? Perhaps it was their way of trying to wriggle out of responsibility? Hopefully I'll find out more when the car is picked up from the company that's fitting the new engine.
The situation with belts and chains can be confusing, but the belt is not the chain and the chain is not the belt. Some engines have one, some the other and some have both. And some even have a belt that is bathed in oil, and looks, from the outside like a chain, but it is really a belt.
In any case, if they changed the belt and what is failed is the chain, I can't see how they can be held to account for that. It is not the part that they supplied and fitted.
That said, a chain failure that early in its life would be an unusual thing. Has anyone expressed an opinion as to why it might have failed so early?