I've found UK media coverage of this row disturbingly one-sided (even amongst pro-EU journalists)

You may want to read this for a more balanced view :

https://www.irishtimes.com/business/health-pharma/dragging-a...

It was really AZ's screw up. The fact is that the EU had a contract with AZ that explicitly required the use of UK plants for fulfilling the EU's orders if need be. But the problem is that AZ had also promised the UK it would have priority over the goods produced on its soil...