To be honest, not being a fan of the stuff, I don’t pay close attention to the differences in that type of food. So, sorry, I don’t know. London has fantastic food now although in the bad old days they had the most wonderful Indian food (and they still do!)
My heyday there was during the nineties. Indian food opened the door for them as you say. Outside London it was pub grub, fish & chips or traditional boiled fare at the time.
Traditional Mexican isn’t as spicy and often not spicy at all. Not so colorful either, although there are regional variants. What we typically think of as being Mexican is actually Tex-Mex.