Not to dampen any hope you have Sam. I know my car takes a different route to yours to get to the dealership, (min is Emden to Sheerness to Exeter). But it stayed at 3 weeks on the In Transit stage of the tracker for about 2 weeks+ before progressing to 10 days on the tracker. If your's is saying 3 weeks then it is most likely sat at Emden docks waiting for a ship, not actually on a ship. I hope I am wrong, but my faith in the accuracy of the tracker and VW info is failing fast.
I have been told that mine is now in the UK and booked to go on a 'Eddie Stobart' Transporter early next week to be taken to the Dealership in Exeter. I cannot wait, but will not believe anything 100% until I see the car in the flesh. I was previously told that VW had 3 ships going from Emden to Sheerness last week and my car was on one of them. This was not correct. My car actually came in to Sheerness this week.
My only advice is to keep on top of your Dealership asking for updates on progress. It is the only way of finding any info at this point. Hope you get your car soon Sam. It is on the home straight now.