Yeah, UK by area is mostly Scotland, which is stunningly beautiful and quite empty. Also infrastructure there tends to be more basic; even main roads in the north of Scotland are often single lane with passing places.
Wales and Northern Ireland are smallish by land and not very densely populated (?) but not massive outliers I'd think.
Even the SE has areas with surprisingly low population density. Outside of the urban areas much of the land is protected against development as national park/AONB/green belt.
Wales and Northern Ireland are smallish by land and not very densely populated (?) but not massive outliers I'd think.