tidal lagoon power plants, page-5

I think you have this wrong Megafauna! They are talking about smallish lagoons in the plural. " Potential lagoon sites are Cardiff, Newport and Colwyn Bay in Wales; Bridgwater in Somerset; and West Cumbria. "
Not sure how much one stretching from Wales to Cumbria would generate but it would probably power most of Europe!
The previous proposed Severn Barrage (which would be huge) has been blocked because of environmental damage (no more mudflats for wading birds), although there are several possibilities which would keep some of the rise and fall.
Just imagine that picture above including (unseen) CWE buoys which are also generating power as well as taking some of the sting out of the waves.