I don't mean to rain on the parade, and I do agree that this is the best burrito I've had thus far in London, but I was not left with an overwhelmingly glowing impression of Mucho Mas. Although the burrito was indeed large by London standards, it was still a bit puny by my own, and there was a decided lack of skill in rolling and wrapping it on the part of my server. I also would have appreciated a broader choice of beans (they serve black beans only), salsas (there are four salsas, which is not nothing, but I found myself dousing my burrito in the hot sauce found on the tables to get more flavor) and other toppings (most notably jalapenos). Although Corona is served, I'd prefer a Negra Modelo or Pacifico any day.
All that aside, this is a somewhat inspired, filling 'San Francisco style' burrito in a cool neighborhood at a decent price (my chicken burrito with all the fixings came to about £5.50). It's clear that the people behind Mucho Mas have studied Californian taquerias as well as the national chain Chipotle and stick to the relatively slick, stainless steel style common to those businesses, and I would not be surprised to see this restaurant successfully expanding throughout London.