Limited resources? The number of packages coming into the country is vast. People have reported grey importers using various tricks such as under-declaring the value of the contents. It's interesting that some of the grey dealers seem to have given up on the UK in recent months, when of course a few things have changed. The new import tax regime is in place and there is no longer a VAT exemption for low-value items. And with the UK now outside the EU Customs Union, packages coming in from continental Europe are no longer assumed to have had VAT levied already. We know that some packages from HK dealers were coming into the UK via EU27 countries. Perhaps they were using routes of entry into the EU where few packages were intercepted, and then, once inside the Customs Union, sending them on to the UK?
But again, if anyone has a receipt from a grey market HK dealer where VAT is itemised, perhaps they could produce it and end the debate?