I also have at least 1 parcel missing from middle of august, which was birthday presents for my boyfriend. My family sent him presents as his family have never made a fuss of his birthday. The strange thing is that my family sent me a parcel on the same day which finally turned up a couple of months later.
My family now have insurance on the parcels and have been claiming from Royal Mail when the gifts do not turn up and purchasing the presents again so we do not miss out.
The last parcel my family sent (easter eggs) arrived in a couple of weeks. Hopefully the problems have now been resolved.