Birmingham Co-Op supplied both types of milk. Those of my friends who had sterilised were in Co-Op supplied families, the 'pasterurised people' had milk from other companies so I always associated sterilised with the Co-Op. going by what I could see on their milk floats sterilised was their best seller.I can't recall who supplied my father's parents (the "sterilised" ones!), but my mother's mother (with whom we lived) and both her sisters worked at the Co-op, and we only ever had pasteurised.