The best thing is to make our own. You need to get maize flour (a good exotic food shop should stock it). When I was in Scotland I always went to a Mexican stockists just above the Royal Mile. They also sold tortilla presses which makes the whole process so much easier. But I digress.
You just add water and you're away. Make then thin and small and make sure your griddle pan is VERY VERY hot before starting. Experts use their fingers to flip them, but I recommend using a spatula for the first few times wlse you'll end up with burnt fingers.
Maize tortillas are the real deal. The flour ones are really a Tex-Mex invention, like most of the stuff that passes for Mexican food in the UK and the US.
But I digress again.
You will like proper tortillas. Packet ones in UK supermarkets bear no ressemblance to the real thing. It's like comparing Tesco value bread to a nice home baked loaf.