How can we maximise collection from PCNs issued in Camden?

Only 18% of all PCNs in Camden are outstanding
Status of penalty charge notices issued to all countries since November 2015


But over 70% of PCNs issued to vehicles from Eastern Europe remain Outstanding

Status of penalty charge notices issued to EU "Eastern European" countries since November 2015

Do other Boroughs collect from vehicles registered to foreign countries more efficiently?
Is additional data available to help collect these outstanding fines?