Mexican food comes from Spain and Mexico shared a culture exchange with Spain. As for ingredients, beans, chili and tortilla's are not ingredients that are hard to get a hold of. So my question stands as it was originally given, why had Mexican food not caught on so well in the UK?
I agree with those posters about the lack of Mexican immigrants as a big part of the reason there is not a prevalence of good Mexican restaurants.
A British friend was telling me that Thai food became popular in the UK, after Thailand became a popular holiday destination. So, using that logic, perhaps another reason is I don't think that Mexico was a hugely popular tourist destination for Brits in years past. However Mr. K and I went on holiday in Cancun last year and half the people at the resort were from the UK. So, I wouldn't be surprised if Mexican food becomes more popular in the near future, as more people visit and enjoy the food.
As for Mexican food and Spanish food...my experience has been that they are totally different. A tortilla in Mexican food is a type of flat bread made from corn or wheat flour and a tortilla in Spain is a potato and egg pie, bearing more resemblance to a quiche than anything like a Mexican tortilla. And Mexican chorizo is nothing like a Spanish chorizo. In my opinion, Spanish food has more in common with its European neighbors than it does with Mexico.
As for finding the ingredients...of course you can find them. But other than flour tortillas, you are not just going to find them on the grocery shelf as easily as you do in the States. And the further you are from a large metropolitan area like London, it is even harder. (Don't get me started on what Old El Paso tries to pass off as corn tortillas.) As my father used to say, if you want something enough, you will find a way to make it happen. The
Mexgrocer site is a great place to start.