Which port is yours going into? Tyne seems to get less frequent ships, Grimsby and Sheerness more regularly. So that may be a factor.
I also get the impression that build allocation and order prioritisation is a factor in which vehicles get shipped when. Was reading the Cali club chat earlier this week and there are examples of vans almost driving straight onto ships when cleared at Emden for export, while others sit idle on the dock.
From the outset of my second order, the dealer was adamant it would arrive around end of March. To be fair it already had a provisional build date as it was a stock order, but he was spot on. I’ve found him far more on the money than VW chat, who never seem to have up to date info.