A British friend of mine always took exception to the stereotype of Britain having bad food, his line was that they had the best food in Europe giving as the example all the imported Indian dishes.
That probably WAS true back in the day. But then again so did NYC. It was still a center of upscale dining but there were essentially no interesting mid-level options.
The Internet changed everything. Someone starts a food trend in Austin, and two weeks later it's on the menus in L.A.
Though, if you did your research, you could find really good, authentic, British cuisine (eg: St. John's).
OTOH, how much of a colonial, shared history do you have to have to accept Indian cuisine as "traditional" in the UK?