I moved from Guernsey (Channel Islands) to Switzerland a few months ago, so this may help.
I drove my car down here, then rented a 3.5 tonnes "white van" in Zurich, drove it to Guernsey, loaded up with boxes, furniture etc... and drove back to Zurich again.
I was stopped at the border in Basel leaving CH with the empty van because the Swiss police didn't believe that it was empty, but they just had a quick look inside and they let me go (well, it was empty...).
On the way back here (full van) I was stopped again, but they literally opened the van doors and closed them again in about 0.5 secs. I was already ruffling up all the paperwork that I was supposed to have (import declarations, bond documents etc...) and they told me to bugger off 'cos I was stopping the traffic.
Not sure if the CH plates on the van helped, or maybe it was my Italian passport (they must see a lot of them going back and forth...). I put it down to the fact that it was 7am and a lot of people going through the border, not sure if they are more thorough at other times.
It sounds very odd that you need to wait 5 wks to import stuff in Holland, surely there must be an internet form you can fill in and bring with you with your stuff at the Douane (that's what they do here...).
you may want to check out
this site