I love Mexican food - used to go to a fabulous tacquera in Sydney, and even checked out a new place when we were home in Feb.
In London, there is not a lot of great Mexican - the exception being the Wahaca chain. I tend to go there when I want to get my margaritas on. Big time.
Otherwise - I go DIY now. I even have a stash of masa harina to make my own tortillas (and although I have a tortilla press, i prefer to just bash them out, great stress relief!)
Oh and the Cool Chili Company have a fabulous stand at Borough market, or I order online from them. Currently have about 8 different types of canned and dried chilies in the cupboard!