'Indian' foods are very much part of the British foodscene and have been since the late 1950s. Today, many of the 'Indian' restaurants are actually owned/cheffed by Bangladeshi nationals, not Indians from India
Much of our food, even from Victorian times has echoes of the British raj - eg the infamous mulligatawny soup and the even more infamous 'Brown Windsor' and for, instance, the old British breakfast standby (now usually cooked as a supper dish), kedgeree - rice, flaked smoked haddock, hardboiled egg and a curry mix.
One of my favourite places in London is Benares, owned by a michelin-starred chef, Atul Kochhar.
Benares Restaurant and Bar, Mayfair, London
Locally in Edinburgh, Tony Singh who owns Oloroso - a really great restaurant - opened ROTI, which used to be centrally based in Rose Street, but he moved it to a more business-based area. It is a good Indian restaurant - but I think it suffers slightly from its own success. Tony Singh was a chef on the RY Britannia and worked in some of the best restaurants in the country before opening Oloroso.
Tony Singh - Oloroso & Roti | VisitScotland | Eat Scotland