Perhaps I've got this wrong. I could have sworn there was something about Britain, Scandinavia and NZ in his Ray-Way Tarp book but a quick scan has failed to find it.
Anyway, British foul weather isn't too bad under a tarp. You know there is nothing the wind is likely to break, although pegs might pull, and a tarp with beaks can be closed off on the windward side, keeping out horizontal rain. In the aftermath of a torrential downpour, I was staggered by two things
1) How dry my cheap, Lowe waterproofs had kept me
2) The high quality of existence with the tarp pitched high (open sides and ends) in a forest glade. My breath was visible, floating one way then back under the tarp, so humidity was high, but condensation was minimal.
There have been two situations where my Akto would have been nicer than what happened under the tarp. The first was on a paying campsite which had turned to a sea of mud (although it looked grassy from a distance). Shutting out the view would have made things more homely.
The second was, of course, major insect trouble. I don't have the netting inner for the Cave and will not get or make one because, by that stage, I might as well take the tent. In New Zealand, possums would be the problem. They get into everything, and getting a bit radical, in his Bushcraft series, Ray Mears, in Tanzania, chose a single skin tent instead of his usual tarp because of hyenas.
By the way, do you know how to get slug goo off a down sleeping bag?