Tesco attracts a large number of customers every day.  There is an ATM there, evidence that many customers find it useful.  A new post box there would be convenient for all customers, some of whom do not have easy access to a post box where they live.  Many years ago I was successful in persuading Royal Mail to erect a post box in a rural location, and gathering public support was vital then - it is vital now.  Please add your name.