I've been to the Flying Burrito several times. The Middlesex St branch is ok. The Cannon Street one however is closest to me and unfortunately not the best in terms of food.
I ordered 3 x tacos yesterday and for £5.95, I was thoroughly disappointed. The tortillas used for the tacos appeared to be gluten-free or something, such was the lack of elasticity and the fact that the filling fell straight through the bottom of it, which left me trying to hold a sloppy salsa flavoured mess. It would be better to either use a smaller form of the flour tortilla they use for the burritos or use corn-tortillas (this will also be gluten-free).
Additionally, for some reason the Flying Burrito start by putting rice on the taco (which I declined - who puts rice on tacos?). The main meats were miserly portioned (there is no portion control as such), though salad was in abundance though I assumed this was to hide the lack of meat. Furthermore, cheese was added without me asking for it, this appeared to be grated cheddar of some description.
Whilst the staff seem friendly and the restaurant is great in terms of layout, display and being comfortable, I would strongly avoid the tacos.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.