I moved here from the States in February and was missing Mexican food terribly. After promising my British pal for months that he was in for a big treat of a Mexican dinner just as soon as I could locate some cilantro, it dawned on me one day that you kooks might call it something different, so I Googled it. Ah. So that's killed two birds with one stone; I can now also cross "find out what coriander tastes like" off my to-do list. So I went to Tesco and bought all the ingredients for a nice Mexican dinner of chicken burritos with fresh homemade salsa, only to discover that plain corn Tortilla chips don't seem to be something you can get in the supermarket here. I ended up making my own out of flour tortillas but it's not as good and I like to minimize the amount of time in my life that's spent frying things in a giant pot of blistering hot vegetable oil.
Was that whole backstory necessary? No. Sorry. Anybody know of a Mexican grocery in SE1, or any other place that you've noticed sells plain corn Tortilla chips (i.e. not nacho cheese or chili spice)?
I found this page, which demonstrates that somebody has done the work of trying out (or findign people who have) every single Mexican restaurant and Mexican food supplier in London. I don't think you can beat that:
Since Elephant is one of the few areas in London to boast significant numbers of people from South America, there must be some "small" suppliers that look like small local grocery shops that sell South American food.
I don't know how many of the locals living in E&C are Mexican, but I figure you could do worse than asking some of the restuarant owners on the top floor of the E&C shopping centre where they source their goods from (if any of them appear to serve Mexican or Mexican related meals).
Borough Market is the place to go -- the Cool Chile Co (www.coolchile.co.uk). Usual in the part of the market next to Southwark Cathedral They even have fresh tomatillo's when in season. I think you can also order online. They also have a restaurant in Notting Hill. Not SE1 I know but I can heartily recommend as proper authentic Mexican and not the usual interpretation you get in the UK (crispy taco shells?!?!)... not connection just a very satisfied customer...
A few weeks ago a new Latin American convenience store called Sol Andino opened at 187 Old Kent Road. Its opposite East Street Library and sells all kinds of Latin American foods - organic quinoa cheaper than the stuff in Tescos...