The big issue I see with this is that the new rules do not mandate any kind of identification on packages that have the VAT already paid, so they can't identify

The big issue I see with this is that the new rules do not mandate any kind of identification on packages that have the VAT already paid, so they can't identify VAT-unpaid packages. And as the seller is now responsible for VAT for B2C consignments under £135, I'm unsure if they can extract the 20% from the recipient anyway. I'm guessing that at least for now this means everything valued under £135 is going to go straight through, and they'll implement something sane later...