I see that folks from England are fixated on Indian curry. Don't you folks expand your horizons into Thai curry?
India was "ours":Thailand wasn't. A lot of British families had lived in India for generations and during the governance of the East India Company their male employees were encouraged to marry Indian wives. Others went out there as servicemen or civil servants or business men during the years of the "Raj". As they had Indian servants, including cooks, they learned to enjoy Indian food and when they returned to Britain throughout the 18th, 19th and early 20th centuries they brought their tastes (and their servants ) with them. The 1901 census shows more than 70,000 Indians resident in Britain comprising Indian seamen, soldiers, diplomats, scholars, officials, tourists, businessmen and students .
The British merchant fleet employed Indian sailors from the 18thC onwards and many of them landed here and, because they were unable to get passages back to India, they settled mainly in sea ports taking such jobs as were available. Many of them were cooks and earned a living cooking for their compatriots. The first Indian restaurant in Britain opened in 1810.
Indian food became very popular in the home from an early date - Hannah Glasse's domestic cookery book, "The Art of Cookery", first published in 1747 included recipes for Indian dishes and Queen Victoria (reigned 1837-1901) had a penchant for Indian food, establishing a special kitchen staffed by Indians to cook it. Actually, "curry" isn't a dish at all. It isn't even an Indian word. It's just a made up word coined to describe a wide range of Indian (and now Thai) dishes. It may come from an old English word for "cooking" which in turn came from the French - there was a mediaeval cookery book called "The Forme of Cury" dating from the 1390s - centuries before the word was used for an Indian dish.
Post WWII, before and after independence, there was a further influx of (usually male) Indian immigration to take up work in various trades and professions and in 1972, when Asians (ie people from the Indian sub-continent)were expelled from Uganda many chose to come to Britain. This all expanded the number and popularity of Indian restaurants and the availability of ingredients for Indian cooking in high street stores.
We were importing foodstuffs and recipes from all over the known world as early as the first crusade in the 11th Century AD.
Thai restaurants are relatively new arrivals to the British dining-out experience but have taken off, probably due to the opening up of Thailand to the tourist trade, and domestic cooking has slowly caught up but it still lags a long way behind the Indian food tradition in Britain.