My parcels arrived finally, after 4 weeks from the UK. I did also, in the meantime, receive an answer from the Royal Mail regarding my complaint :

Dear Mr
Firstly, may I apologise for the annoyance and inconvenience you have beencaused. I do understand how frustrating it can be when items of mail arenot delivered in accordance with procedure. Royal Mail is not complacentabout the level of service we provide and we are continuously looking atways to improve the service that our customers expect from us. If I may explain about Airmail items. We do not trace Airmail itemsthrough the system. With millions of items travelling at one time it isimpossible to determine where your items have gone astray. I was also disappointed to learn of the problems you have experienced andyour general dissatisfaction with the standard of service you have beenreceiving from Royal Mail Netherlands (RMNL). May I first give you somebackground information concerning mail deliveries to the Netherlands. TheUK send mail on a daily basis Monday to Saturday to the Netherlands and itis delivered by either TPG or TNT (Dutch Post Office). The ManagingDirector of our delivery agent RMNL has reviewed delivery arrangements inlight of recent complaints. He has identified some issues with RMNLdeliveries in the Rotterdam area stemming from problems with holiday-coverand temporary workers. He assures us that steps have now been taken toresolve this. Selektvracht is also used as a sub-contactor by RMNL, butRMNL can identify no significant quality issues using feedback from theirown quality control measures. There has been no recent change to theoverall arrangements for mail from the UK to the Netherlands and measuredend-to-end quality from the UK to the Netherlands has been on an improvingtrend. We had a recent performance review with the delivery agent in theNetherlands and no major quality issues were evident. I also contacted our Network Manager for the Netherlands Alex Obradovic.Alex has contacted his counterpart responsible for handling items into theNetherlands to ask if he can offer any explanations for the upsurge incomplaints. Unfortunately our contact in the Netherlands is aware that TPGand TNT have been going through a major change recently but we have noindications that this has affected delivery quality. I would like to assure you that the security of our mail is of paramountimportance to us and for this reason the details of all losses are loggedonto our internal computer system and sent to our Security andInvestigation team. They use the information to assist with highlightingproblem areas and identifying trends and patterns relating to losses in thepostal system. I have of course passed on your details. I am sorry that my reply is not more conclusive; I would like to think thatall our customers can rely on our services with complete peace of mind andI can only offer my sincere apologies for the inconvenience caused. If Ican be of any further assistance regarding this matter, please do nothesitate to contact me and I will be happy to help. Yours sincerely Deborah Warren-GriffithsRoyal Mail Headquarters cc Alex Obradovic