It's also a lot cheaper to buy even in bulk as we
would need over 100 plants - so why is that? Are there any major
differences between hornbeam and beech that we need to know and haven't
discovered? Is hornbeam less fussy and a better grower or something?

Can't say i'm an expert in such matters but I have heard often that Hornbeam
is tougher and more resilient than Beech when it comes to such things as
drought and diseases like Honey Fungus. I heard also that there is some
newish fungus going around that can destroy Beech very easily. We have a
predominantly Beech hedge at the front of our property and I want to figure
out how to underplant with Holly.

Sam