On the first Monday I went on the 11:45 Paddington - Swansea. But only as far as Reading.
I was in the front 5 car unit, there did not seem to be very many toilets and at first the disabled toilet was locked out of use, although later the train staff reopened it, saying that there had been an issue with the door.
I thought that the First class interior was nicer than the standard class, but I suppose that this is to be expected.
Despite the high number of seats Standard class did not seem that cramped, although I suppose that it helped that the train was not full. With Japan also being a well-populated nation with many crowded cities the Japanese are of course masters in building high-density trains, even for longer distance routes.
Below is a film I made showing this train.
btw something that I decided to not include in my film was my getting a finger caught in the internal door when it fully opened after the lady walked through it.
Simon
edit to add: a few errors crept into my first version of this film so it has been replaced with a second edit.