I spoke to a friend of mine who used to work for a shipping company, who gave me a bit of insight into the kind of operations involved here.
In essence, time is money and space is money, so they won't be keeping your car at a port at either end for any longer than they can help. All being well, that would mean your car will be loaded onto the next available ship. However based on delivery to Chelmsford, the Schelde Highway isn't the likely boat because that's only been doing round trips between Emden and Grimsby, and Grimsby isn't used for anything in the south from what I've read. The next paragraph assumes VW would rather your car be delivered to the correct part of the UK - if they really want your car out of Emden port then your car would be on the Schelde Highway.
You'd be needing the next boat to Sheerness in Kent, which is smaller than Emden so there's even more motivation to get the cars shifted at the other end. This means you're looking at either the African Highway which is on it's way back to Emden from Grimsby at the moment, or the boat Emden which is docked at Sheerness. As Emden has been doing round trips between Emden and Sheerness lately, I'd predict your car would be shipped on Emden once it returns to Emden port (which would be late tomorrow or early Sunday I'd guess).
From what I've been told, the ports themselves will be 24x7 but it's the logistics companies that process cars delivered to the ports and transport the cars onwards to dealerships that tend to be more Monday-Friday operations.
When did you get the 5a alert then? I got mine on Tuesday morning at 8:45, and got the 5b alert exactly 48 hours later, while Emden the ship was still docked at Emden the port (slightly confusing) - it would seem for the shipping phase that things get updated in batches rather than in real time.
I'm not going to pretend I understand the nuances of VW's logistics but I'd say on the whole VW want to get the car to you ASAP because the sooner you take delivery, the sooner the money comes in for them for the car they've already spent many thousands of pounds lovingly manufacturing for you. Fingers crossed for you that it's on its way to you soon!
