Pro tip - any restaurant that serves Balti and Tikka Masala are not Indian restaurants, even if owned by Indians.
Even when they have a full menu of stuff with names of dishes from India, its still all a variation of a British Tikka Masala or such. None of the food they serve is authentic Indian food.
For starters most Indian's are vegetarian. There was an attempt at a genuine Indian vegetarian cuisine restaurant in Bradford, which went out of business very fast.
Vegetarian food appeals to very few people in the west as generally people want either meat or vegan.
And honestly, a proper made British curry with all fresh ingredients wipes the floor with taking months old expired vegetables and cooking them with spices to mask the rot.
As you say, i'd be very surprised if there are m(any) genuine Indian restaurants in the UK, as they'll need to cater to their main audience.