Canoeing across the UK's three east-west urban corridors

The UK is well known to be far taller than it is wide.

Actually it is surprisingly narrow in three places and correspondingly rather wide in three others.

It is almost as if the UK is made of plasticine and when it was pinched tight between Bristol and London, Liverpool and Hull and the river Clyde and the Firth of Forth, the areas immediately north and south of those narrow waists expanded into wide hips.

Viewing the UK at night from space reveals that the three narrow waists are almost one big smear of lights from interconnected big urban centres while the three wide hips are darkish with only scattered lights and hence particularly underpopulated.

This is why I say the north-south urban corridor in the UK runs through only three real mega cities( London to Manchester to Glasgow) because each of those three cities are the the biggest city in its own east-west urban corridor.

So adventurers love to canoe from Liverpool to Hull, from Glasgow to Falkirk, from Bristol to Reading ,from the west coast to the east coast (or vice versa) overland by water : starting at a big estuary, along rivers and canals to a big estuary on the other side.

Maybe a short portage or two or three along the way.

Certainly communities located in the wide hips have a hard go being connected east-west, mostly because they don't have the flat terrain that two linked east-west big river-estuary watersheds naturally provide.

Some of the British rebels running their own DIY penicillin ops during WWII were located in the wide hip areas off the main corridors of political, commercial and academic influence, hence my interest in what might seem arcane spatial geography.....