It's a right of passage for everyone who orders, Tesla tell you nothing of any value or accuracy until you get into the final weeks - contact them ten times and you'll get ten different answers about what's going on.
As a general rule of thumb they try to deliver all vehicles by the end of the quarter, so the first week of April may inaccurate depending on whether it goes to the leasing company first or direct to you - if it's going directly to you then end of March is more likely if your car is built in Q1 this year, if your car is built in Q2 then forget April, those cars won't arrive until mid to late May.
If Tesla have your email and mobile number then you will get a message when you have a vehicle allocated, generally those come any time from when the car is at the dock to when the ship clears the Panama Canal. After that you have another few weeks to wait until they send you a follow up scheduling pickup/delivery and then another with your VIN and Reg about a week before you get it.
Follow Mr Miserable's shipping thread when it starts up again, you should then be able to work out which ship you are on from your allocation message timing and that'll give you a more realistic ETA in the UK; your delivery will then typically be 4-12 days after it gets to Southampton.
