Do you have a source on that? I was under impression that the UK manufactures their entire AZ stock and the only vaccine produced in the EU for the UK is Pfizer/BioNTech

The UK doesn't quite manufacture its entire supply of the Oxford/AstraZeneca vaccine - some is imported from India, and apparently one small batch was from a factory in the Netherlands which doesn't have enough production capacity to make much of a dent in the European demand: https://www.bbc.co.uk/news/56483766 But yeah, the vast majority is apparently locally manufactured.

The EU has been pushing the conspiracy theory that the reason there's a shortfall in supply of the AstraZeneca vaccine there is because they've been exporting it all to Britain, but there's no evidence for that which anyone can find and the numbers don't add up either.

70% of the doses the EU bought were instead delivered to the UK to fulfill AZ's obligation to the UK.

After that initial batch, a further 8 million EU doses were exported to the UK, and a further 46 million EU doses were exported to other countries, including the US.

Just this second batch would have tripled the EU's vaccination rate so far.