Yes, I had looked there with the same feelings as you. There are some cheaper used but would prefer the reliability of a new unit, I think? How reliable is the class 20 if I were to go for used, I wonder?
That's reassuring, David, doesn't sound like too much work to get them to mate together. Are the bogies on the Class 20 correct for the Hunslet? Will probably bide my time at these prices and get one with yellow detail on the bogies sides, should be easy to blacken it out