There's a bunch of stalls around Newport Place and Little Newport Street. The one next to the Tianjin crepes stall (http://chowhound.chow.com/topics/870574) sells steamed buns, Taiwanese savoury "pancakes" and "pork kebabs" aka 肉夹馍 which are actually sandwich-like rather than kebab like, meat filling in a wheat-based bread.
The bread is substituted with what resembles a toasted English muffin, heated on the griddle, sliced in the middle and filled with braised bits of pork that were delicious with meaty and fatty bits tender and slippery, flavoured with nuanced chilli heat, a dark umami from soy and bean sauces, and levity from crisp aromatic coriander leaves. A very tasty treat for £2.50.
Bunch of other stalls that seem to vary over the months. Besides a second Tianjin crepe stall, there's another okonomiyaki/takoyaki/taiwanese oyster omelette stall as well.