@PigletJohn
The EU has behaved very unreasonably.
EU has sent over nine million doses to UK
UK has sent zero doses to EU.
Yep, there's certainly somebody not being very co-operative.
But who is it?
Does anybody, seriously, expect that pattern to continue?
That's not how these things work, is it? It's not like disaster relief aid where a government pays for and sends supplies across to another nation, the EU has sent nothing. Private companies happen to be in the business of trading across borders, nothing to do with governments. The UK had contracts with the likes of AZ and Pfizer to produce vaccines. Some of these happened to be produced in EU member states. Nothing to do with the EU, entirely to do with supply chain decisions made by private companies.
The EU also had contracts with pharmaceutical firms. These firms have not yet used UK factories for these contracts because those factories were already committed to other orders. There are however some UK factories involved in the supply chain for EU orders though.
There of course came a snag where a private company was struggling to fulfil its order to one of its customers. The customer went "can't we have some of another customer's order to keep us going?". That couldn't be done because the other customer had signed its contract under English law which offers far better protections to the customer than Belgian law. Therefore if the private company had allowed political pressure to divert its product, the second customer would have been able to invoke penalty clauses. The first customer on the other hand (the one who signed under Belgian law) can't actually do any more than withhold payment.
At no point should any of this have anything to do with UK-EU relations. It's all between private companies and their customers. Neither party has any need to "be cooperative" with the other on vaccines because issues between the EU and one of its suppliers are not any of the UK government's business, and vice versa.
In a populist tantrum, UvdL has threatened to interfere with the legitimate passage of goods between supplier and customer. Doing so would collapse commercial confidence in the EU, causing manufacturers to rethink whether they can trust the long-term stability of the bloc when the circle of stars have effectively been replaced with the Jolly Roger. This comes on top of the same individual moving to close the Irish border just in case the UK should attempt to engage the Hawkhurst Gang to smuggle doses into the UK that way.
(If anyone thinks that my pirate and smuggler analogies are a little preposterous, that's exactly how ridiculous UvdL's behaviour is)