1.retention the customer is so important inside of whatever business because is more  expensive try to attract new customer that keep  the loyalty and satisfaction of  them .  

2. Morrison has several important difference with it's competitor...

they handle an interesting approach ... holds great control of its supply chain known as the "field to fork" approach ,for this they have more control about the quality of their products.
they are offering the freshness of the products at its customer  as nobody can do it as them... because they try that fresh produce is sourced locally wherever possible, which is then processed in morrisons own manufacturing facilities .with which they can achieve to offer its products more fresh than its competitors..

They provide the best customer service this is possible thanks to Morrisons has invested heavily in training and developing colleagues to generate its high quality customer service..  which is translate in ...helpful and friendly employees deliver an exceptional checkout experience to help retain customers.

Morrisons achieves  offering products and services, , that are not offered by its competitors therefore they achieves maximising customer retention.

Customer service is the clue of the differentiation with the competitors when the consumers get a personalised  High quality customer service from a trained professional  all of this help to becoming them in loyal customer and retain them at the same time.