I'll be doing the North Sea Route in the spring and I've been told much of the North West European shoreline doesn't have a lot of good size trees to set up my Hennessy hammock. In the three years I've used the Hennessy I've never had to use it as a tent.

Has anyone done this? Will I need poles? How about stakes? Will I need something like a Thermarest?

You do need poles, and I would suggest a pad.

https://www.hennessyhammock.com/use-as-a-tent.htm

I have a hammock as well, but choose to take a tent for my trip to yellowstone. 700 miles of Kansas and CO. with no trees.... I have tried the tent/hammock method before and hate it.

REI has some carbon trekking poles that are under a pound for the pair of them. For a while you could find a lot of them on Ebay for cheap since employees were prodealing them off the sales floor and auctioning them off. I use trekking poles with one of my tents and they are much stronger than regular aluminum poles.

This is a great link, but I can't really see from the photo, or figure out from the text exactly how it is done. It does seem that you need a couple of guide wires on either side and the fly seems to be separated from the hammock a little more than usual.

I guess I'll have to get a stick and experiment before I leave.