What's wrong with their aesthetics? I've always found their simple design to be quite nice.
They had an analysis showing how many % of their visits had broken JS support and therefore the need to build for the lowest common denominator.
When a team builds a service using the service manual as a guide so many things become so much easier.
Need to explain something to a non technical manager? The service manual has got you covered:
> Progressive enhancement is a way of building websites and applications. It’s based on the idea that you should start by making your page work with just HTML, before adding anything else like Cascading Style Sheets (CSS) and JavaScript.
A great principle, and nice to see they even think about Lynx accessing the sites [0]
The post I was thinking about with the analysis of why JS/CSS shouldn't be assumed to work was [1].
[0] https://technology.blog.gov.uk/2016/09/19/why-we-use-progres...
[1] https://gds.blog.gov.uk/2013/10/21/how-many-people-are-missi...
Addendum: plus being accessible (essential for any govt. service).