One of the best sites to 'do stuff' in the UK is gov.uk
I've just filled in a new ESTA application on the US gov site too, simple (albeit stupid), and worked.
This morning however I tried using enterprise b2b to book a hire car, it took 6 attempts before it actually worked. Almost all corporate tools seem to be terrible.
To be frank, the government has issues making things usable, and "usable" is a pretty small target when you're talking about the entire US workforce.