In the meantime, the R package 'eurostat' has come along, so I've converted to using this to exploit Eurostat's newish bulk download interface. (Again time-out problems trying to use anything like a filter on this - suggestions are welcome. Could be linked to firewall issues at work but no time to investigate this.)
Anyway, the pax data are now updated (using avia_par_xx). 2015 would be complete, but Poland is missing Q4.