I just want to point out that there is practically no way to identify a "real" Indian restaurant unless you've lived in India for a while.Have I hit a nerve or something?
There are much nicer, real dishes out there which a guarantee you would prefer.
So most of us, myself included, wouldn't know the difference between so-called British Indian dishes and Indian dishes. Seriously, it's very nearly an impossible ask.
About the only thing we can do is decide if we like something or not. Knowing if it's "authentic Indian" is not a reasonable ask.