It's more complicated than that. UK -> UK transactions are capped at the same rate as they were pre-brexit. That was codified into UK law. The problem here is

It's more complicated than that. UK -> UK transactions are capped at the same rate as they were pre-brexit. That was codified into UK law. The problem here is that Amazon UK, the part that the consumer pays at least, is _not_ a UK company, it is a Luxembourg based company. Therefore, there is no cap because from their side it is an EU -> Non EU payment received, no longer an intra EU payment. These types of payments were never capped by the EU. So yes, Brexit caused this, but then, given that other companies do seem to be able to take payments in the UK, and that all of their physical UK operations take place in the UK, perhaps they could have avoided it by re-locating the payments to the UK. Except, I do think that may have meant attracting a higher tax bill. Honestly, making it difficult for companies to relocate their profits to a tax haven could be regarded by some as a feature of Brexit, instead of a bug.