The Ouse is a bad example. it has been on sale for over a year and reduced!
The navigable Ouse is very short, just a few miles, Possible permission to build a jetty but the Ouse floods nearly every winter, this February right up to to the railway lines, 2002, right into Lewes itself causing much devastation which the town is still recovering from!
This mooring from what I can work out is very near the town and not where I personally would want to moor a boat. Believe me I would snap it up myself if it was worth the money!
Edited to add that it looks like they have built the pontoon now!