Here's a couple of pictures. I don't know what metal the exchanger is made from. Also, I wasn't planning on doing any of this myself, I don't know how to weld or commission it back to working again. Wondered if it was possible. The leak seems to be from the front bottom corner as far as I can tell, it's difficult to see. With a bill for approx. 3500 to supply and fit a new one I wanted to investigate all possibilities first.