According to the Royal Mail site, PDDP is currently available for;

Austria
Cyprus 
France
Germany
Luxembourg (PDDP service only available up to 150 euros)
Malta
Netherlands
Norway
Portugal (Coming soon)
Switzerland
Sweden (Coming soon)
The Republic of Ireland
United States of America 

Unforuntately, only the USA seems to be covered in Click & Drop.

With the new customs duties on low cost goods introduced by France and Italy - we need this facility, as you cannot account for it via IOSS, and we have no control over whether goods sent to Europe go through France or Italy as the port of entry!