Ap Lei Chau main street. You can choose your favourite seafood at the market and then bring to the food store just upstair and eat there. It's much much cheaper at lunch time than dinner.
may still have at 7pm but limited choice(is the market closed at 7:30?? sorry can't remember), better go before 6:30, you will buy things at a very economic price!! once the market closed, you shall go to the food store at another entrance (very easy to access), hope you will enjoy!