It depends how they are sent. If they are sent "Tracked" then Parcelforce usually hands them over to SCS, a European courier service, and from SCS to ACS in Greece, a local Greek courier service. If you put the Parcelforce tracking number into the SCS web site
it should give you an SCS tracking number. Once you see that the parcel has arrived in Athens you should be able to get an ACS number and entering that on the ACS web site
should allow you to see where it is. If it is not tracked then it will probably be delivered by ELTA to your local post office. That's my experience but, of course, companies do change with whom they do with business so it may have changed.