I emailed Tesla about my order, and got the following reply.
You may have seen that today Model 3 Performance vehicles have appeared in our inventory. All of our existing orders, included yours have now been assigned a vehicle, and the team are going to procedurally work through these.
The vessel has a confirmed arrival date in the UK now in the first fortnight of June, and you will therefore be offered a slot to collect your vehicle in the second fortnight of June. We are on the home stretch as such now!