Disclaimer: my trademark law knowledge is limited to the US, and UK trademark law may be very different. But it seems to me the real problem is that the UK trademark authority granted a registration for Taqueria rather than rejecting it as merely a descriptive term, albeit in a language other than English. It’s like allowing a restaurant to claim exclusive rights to use Pizzeria or Café.
There was a place on 8th Ave. in Chelsea (Manhattan, not London) called Food Bar. Imagine the possibilities!