Bookmaking suppliers list and List of (Mostly) Online classes

For making your own bookcloth: The generic name for what I've been using is fusible web. I think Vilene is the best manufacturer in Europe (honestly, probably better than Pellon here!), they do have a store finder for the UK: https://www.vlieseline.com/Grossister

It's often used to stabilize fabric for appliques, and so often comes with a paper backing when sold by the yard or in larger packages. But it's also sold as hem tape, etc with no backing, in which case you can put a piece of paper behind it when you iron it on to keep it from sticking to the iron.