@trev As @Moem has so succinctly remarked, indeed it is! If you had succeeded in running Pi Hole on your device, you would have then have to proceed to set your device as your network's DNS server, which would mean that you would have no DNS, and consequently in practice no internet, if your device was offline for any reason at all. In short, I don't think running pi-hole on it would have been a very good idea.

Genius! That worked a treat. Well, I've gotten the Netherlands one working. And the USA one is taking much longer to fail than it used to! I'll count that as progress.