Complex sentence: Traditionally, the cleaning process was carried out at centralized factories; high street cleaners' shops received garments from customers, sent them to the factory, and then had them returned to the shop, where the customer could collect them.
Split into simpler sentences: Traditionally, the cleaning process was carried out at centralized factories. High street cleaners' shops received garments from customers, sent them to the factory, and then had them returned to the shop, where the customer could collect them.