In the UK, if you talk about 'Curry', most people would instinctively assume you were referring to food from India, Pakistan and Bangladesh, as Chicken Tikka Masala and Chicken Korma are widely named as the most popular dishes over here. A lot of the popular Curry dishes in the UK were created by migrants in UK restaurants and it is generally considered not to be that 'authentic' and is largely based on the food from North Indian and Pakistani cuisine. Nevertheless, some of these restaurants are completely fantastic and the level of skill and knowledge that goes into the preparation of the food is highly remarkable.
Recently, I have been going to a restaurant near where I live, which is generally on the cheaper side of things. It has a large contingent of Indian clientèle and I believe it specialises in Southern Indian food. Many items on the menu, I have never seen anywhere else, such as Dosa's
http://en.wikipedia.org/wiki/Dosa