Have you slept in a hammock before? I found a sleeping bag in a hammock to be kind of a pain, and not terribly warm underneath. In all but the warmest weather, I like quilt or some insulation underneath the hammock. Then another quilt/blanket to drape over you inside the hammock.

Can't speak directly to hammock camping in Europe. I did read a few Crazy Guy journals of people doing it. At least one of the people had to sleep on the ground at least one night, but was able to hang the hammock most nights. Still, that info may not be relevant where you're going. Might be worth checking to see if there are any hammock camping tour diaries for those areas.

Someone also makes a portable hammock stand. It's on my wish list, but I haven't tried it. And, of course, it adds to your gear, which detracts from part of the appeal of hammock camping.