I've never been to Japan, so can't comment on how authentic anything in the UK is, but ...

We have 'wagamama' which at best can be said to be japanese influenced, and a few chain sushi places (like Yo Sushi) across the country. They really aren't all that great. But if you look at some of the smaller/independent Japanese places that are around and about, they seem to be far better quality. I think London probably suffers from its centre being dominated by chains.

But on katsu ... I've had Chicken Katsu Curry in the UK, sure, but also in Australia, in Singapore and in Bangkok. If that's not a big thing in Japanese Cuisine then quite a lot of the world might have grasped the wrong end of the stick!