Snap a chain on a 240d engine is almost a gaurantee of collateral damage. there are no hydralic lifters to give a little even. Have a look to see if the cam towers broke. If you where able to turn the engine over with the chain broken the clearance to do so had to come from somewhere. These engines are a heavy interference design.
I agree the engine was probably pretty good. It would not happen on a marginal engine. At least to me. Things just seem to work out that way unfortunatly.
Just re read your post. If the chain let go when shutting off or initially starting up there is a good chance it just needs a new chain. Volkswagons diesels will do this quite often and you get away with it. If it broke while actually running past a cold idle is another story.
It was running when you shut it down and refused to turn over to start. I suspect you might be very lucky. I would roll in and time a new chain using a temporary link. If the engine is still good install a new link permanently. There is a better than fifty percent chance you will get away with this in my opinion.