200 Roman, Etruscan vases seized

A 'noted Turin collector' had a collection of over 200 Roman and Etruscan vases dotted all over his living room say police who seized them after the man died last week of natural causes: 

The vases and ceramics, dating to between the VI and the III centuries BC and worth over 300,000 euros, will shortly be put on public display, authorities said. 

So, how many British back bedrooms full of undocumented artefacts of unknown provenance will UK police be raiding as non-reporting metal detectorists pass away? What happens to the products of so-called 'responsible detecting' and the finds of 'nighthawks' when they die? Do they just end up indiscriminately mixed on the market? How can buyers ensure artefact bought on British market of portable antiquities ensure they are 'clean'?  Let us recall that documenting transfer of ownership of portable antiquities from the landowner to the finder was one of the recommendations of the 'Nighthawking Report', what progress has been made putting it into action as part of 'best metal detecting practice' by the PAS and other supporters of 'responsible artefact collecting'?