Can’t beat the experience that is Won Kei and it meets the requirements
I do remember them getting shut down for what they told me was “financial irregularities” but I know for a fact that unless they had rats in the kitchen doing the books, it was more down to hygiene. That said, I’ve been back loads of times and never once been poisoned, the food is decent and quick too.
Other places I like for reasonably quick eats:
1, Bodeans – Poland Street (close to Oxford Circus). American style BBQ
2, Busabi Eatthai – Wardour Street
3, Wahaka – Covent Garden. Mexican that, whilst not as good as it should be (and not as good as Taqueria in Notting Hill) is still decent
Oh and for REALLY cheap food, go to ECO pizza (there’s a couple in the centre). Cheap, quick and good.