been a lurker around here for a while. I'm originally from Portugal and since I moved to London I had a lot of trouble finding Seitan (I get a lot of crazy staring when I mention 'satan').
I've found mock duck on some asian food store which is sort of similar..
But I just discovered real seitan at planet organic http://www.planetorganic.com/
(near liverpool street station) haven't been there yet but just letting everyone know to see if they start stocking it a lot and maybe it becomes more common :-)