Now I don't want to get anyone unduly excited but we recently found a little organic shop on Holloway Road, near the Highbury end, which had a sign in the window saying "Mexican Food" ... we went in and couldn't find anything Mexican but we asked the woman who was working there (Stu thinks she was not Mexican but from elsewhere in S. America) - she said she hadn't been able to get hold of the "Mexican guy" recently but was hopeful she would hear from him soon and suggested we check back in a couple of weeks. So we'll probably pop by and see ... just thought if anyone else was in the area and knows the shop I mean they might like to pop in as well - I got the feeling that if the demand was high enough she would find the Mexican guy fairly quickly.
Also if anyone is keen on other kinds of South American cuisine, there seem to be various cafes further up Holloway Rd, near Holloway Rd station - I think I saw a Peruvian place and Chilean.