A radio article (about the first indian restaurant in the UK, opened in 1810) reminded me of the old chestnut about how "indian food" in the UK is nothing like food eaten in India or in Bangladesh.
It's quite an old mantra. Chicken tikka masala (the most popular dish in the UK, and fast spreading throughout the world) was invented by Bangladeshi chefs (in the 1960s, according to Wikipedia) specifically to cater to the tastes of British diners. Madhur Jaffrey once wrote quite vehemently against the balti, saying that "balti" meant "bucket" and just didn't exist as a dish. (She's changed her mind, apparently, since she now not only sells Madhur Jaffrey Balti Sauce, but also Madhur Jaffrey Balti Dishes.)
The onion bhaji, too, has an unknown provenance. "Bhaji" refers a type of curry made with vegetables, so the reason that in Britain we have traditionally used it to mean a deep-fried onion snack is completely mysterious. (Some kind of clerical error?) A more appropriate indian term would be to call them onion pakora. Although, having said that, indians don't typically make onion pakora - they prefer to use other vegetables such as aubergine.
Other dishes have just been slowly modified. The name "vindaloo" refers to wine and garlic ("Vinho de Alho"), but its firm place in Britain's cultural fabric is as one of the hottest dishes you can order. Even hotter is the "phaal", and although I haven't found much evidence about this I expect it was simply invented for to cater to the chilli-bravado that you often get when a group of blokes go to an indian restuarant.
Anyway. Far more interesting than being smug about our knowledge of what's indian and what's not, would be to find out where, when and how these new cultural traditions arose in Britain. Are there any books or research papers about the subject? Do we know exactly how curry came to be associated with rice (since indians typically have theirs with bread)? Are there any clues about the mysterious onion bhaji?